Facoltà di Scienze e Tecnologie Università di Camerino INFM-UdR Camerino

Camerino, 5-8 Luglio 2004 Università di Camerino

Laboratorio di Mineralogia

Università di Camerino

Libro degli Abstract a cura di M. Minicucci e G. Giuli

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Con il patrocinio di:

Facoltà di Scienze e Tecnologie

Università di Camerino

INFM, UdR Camerino

Invited Speakers

F. Farges, Université de Marne la Vallée (F) M. Kiskinova, Sincrotrone Trieste (I)

R. Rueffer, ESRF, Grenoble (F) D. I. Svergun, EMBL, DESY, Hamburg (DE)

A. Zecchina, Università di Torino (I)

Comitato Scientifico G. Artioli, Università di Milano

C. M. Bertoni, Università di Modena M. Bolognesi, Università di Genova A. Franciosi, INFM-TASC, Trieste B. Martorana, Università di Palermo

S. Mobilio, Università Roma Tre C. R. Natoli, LNF, Frascati

G. Paolucci, ELETTRA F. Parmigiani, Università di Brescia

M. N. Piancastelli, Università di Roma "Tor Vergata" P. Perfetti, ISM-CNR, Roma

S. Quartieri, Università di Messina F. Sette, ESRF

G. Stefani, Università di Roma Tre G. Zanotti, Università di Padova

Comitato Organizzatore

A. Di Cicco, Università di Camerino R. Gunnella, Università di Camerino R. Marassi, Università di Camerino

E. Paris, Università di Camerino S. Stizza, Università di Camerino F. Boscherini, Università Bologna

R. Felici, INFM-OGG c/o ESRF, Grenoble A. Pavese, Università di Milano

I. Pettiti, Università di Roma "La Sapienza" G. Stefani, Università di Roma Tre

N. Zema, ISM-CNR

Segreteria del convegno E. Paris, Università di Camerino G. Giuli, Università di Camerino

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Il comitato organizzatore desidera ringraziare tutte le persone che hanno collaborato, spendendo tempo e pazienza, per

l’organizzazione e la realizzazione del XII convegno della SILS.

Angiulli Gabriella Calzolaio Marta

Cicconi Rita Cinti Marcella

Cottone Claudio Fabbrizio Alessandro

Minicucci Marco Nobili Francesco Piermattei Marco Principi Emiliano Rocchegiani Luca

Santini Marzia

Si ringrazia il Dipartimento di Scienze della Terra ed il Direttore, prof. Gino Cantalamessa, per l’ospitalità offerta nell’ambito del

convegno. Un ulteriore ringraziamento è rivolto agli sponsor che hanno

contribuito alla realizzazione dell’evento.

VACUUM SCIENCE

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XII SILS meeting Camerino, 5-8 july 2004

PROGRAM

Pre-congress session “Synchrotron radiation and Earth Sciences” Monday 5 July – Dip. di Scienze della Terra – Universita’ 14.00-15.00 registration 15.00-15.30 opening and welcome 15.30-16.30 A. Di Cicco (Universita’ di Camerino)

“Radiazione di sincrotrone: una sonda per la materia in condizioni estreme” 16.30-17.30 A. Mottana (Universita’ di Roma Tre)

“Applicazioni della spettroscopia d’assorbimento dei raggi X da radiazione di sincrotrone nella mineralogia applicata al recupero ambientale”

coffee break 18.00-19.00 F. Farges (Université de Marne la Vallée)

“Water in silicate glasses and melts of environmental interest: from volcanoes to cathedrals”

Discussion Tuesday 6 July – Dip. di Scienze della Terra – Universita’ 8.00-9.00 registration 9.00-10.00 A. Pavese (Universita’ di Milano)

“Equations of state and field of stability of minerals by high pressure synchrotron radiation powder diffraction”

10.00-11.00 B. Poe (Universita’ di Chieti) “Structure and dynamics of silicate liquids at high pressure”

coffee break 11.30-12.00 D. Malferrari (Universita’ di Modena)

“Determinazione dell'intorno atomico di Cu, Cd, Hg e dei complessi organometallici Cu-, Cd-, Hg-cisteina adsorbiti montmorillonite e vermiculite".

12.00-12.30 G. Pratesi (Universita’ di Firenze) “Vetri naturali in condizioni estreme: studio strutturale di tectiti e vetri di impatto”

Discussion

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SILS meeting Tuesday 6 July - Sala della Muta – Palazzo Ducale 14-15 registration 15.00 15.30 opening and welcome 15.30-16.15 F. Farges (invited talk)

"Archeologica l applications at the synchrotron: prehistorical paintings, medieval glasses and... baroque musicology”

16.15-16.35 A. Nucara “SINBAD and SISSI, the new infrared beamlines at DAFNE and ELETTRA”

16.35–16.55 R. Gunnella “Structural study of 1,4-cyclohexadiene adsorption on Si (001) surface by low energy photoelectron diffraction”

coffee break 17.30-17.50 V. Carravetta

“Photoelectron angular distribution by resonant auger decay of core_excited H2O: experiment and theory”

17.50-18.10 G. Giuli “Effect of oxygen fugacity on V structural role in synthetic basaltic glasses: a XAS study at the V, Ti, and Fe edge”

poster session wine tasting Wedsnesday 7 July - Sala della Muta – Palazzo Ducale 9.00-09.45 R. Rueffer (invited talk)

“Application of nuclear resonance scattering to the study of nanoscale materials”

9.45-10.05 M. Merlini “The early hydration of Portland cements investigated with synchrotron radiation x-ray powder diffraction (SR-XRPD)”

10.05-10.25 R. Gotter “A novel configuration for multi-coincidence technique and its application to double photoionization in solids”

10.25-10.45 A. Martorana ”Debye function analysis of synchrotron XRD data: stacking faults and microstrains in spherical palladium crystallite “

coffee break & poster session

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11.15-12.00 A. Zecchina (invited talk)

“Zeolitic and silica supported catalysts studied by synchrotron radiation” 12.00-12.20 L. Ottaviano

”X-ray absorption spectroscopy in MnxGe(1-x) diluted magnetic semiconductor: experiment and theory”

12.20-12.40 G. Pratesi “c/a anomalies on cadmium: an X-ray diffraction study”

12.40-13.00 M. de Simone “Variable photon energy PES of M(BH4)4, M=Zr, Hf, U: study of the role of f orbitals in chemical bonding”

lunchtime break 15.00-15.45 D.I. Svergun (invited talk)

“Synchrotron small-angle X-ray scattering studies of biological macromolecules in solution” 15.45-16.05 F. Evangelista

“Electronic and vibronic structure of copper-phtalocyanine: a gas phase and molecular solid study”

16.05-16.25 L. Giachini “X-ray absorption studies of the local environment of zinc atoms bound to the bacterial photosynthetic reaction center”

coffee break & poster session 17.00-17.20 F. Comin

“Status and future developments of ESRF” 17.20-17.40 G. Paolucci

“Status and future developments of ELETTRA” 18.00-20.00 SILS members meeting 20.30 social dinner Thursday 8 july – Sala della Muta – Palazzo Ducale 9.00-09.45 M. Kiskinova (invited talk)

“Spectromicroscopy at Elettra: recent achievements and new projects” 9.45-10.05 F. Da Pieve

“Photoelectron–auger coincidence study of Sn/Ge (111): role of the magnetic sublevels discrimination”

10.05-10.25 L. Pasquini “Vibrational properties of nanocrystalline Fe studied by nuclear inelastic scattering”

10.25-10.45 F. Offi “Bulk sensitive photoemission: design and first results of a novel high resolution spectrometer”

coffee break & poster session

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11.15-11.35 C. Battocchio

“Nexafs study of a pt-containing rod-like organometallic polymer (Pt-debp) deposited onto hopg, Au/Si(111), Cr/Si(111) and Si(111) surfaces: molecular orientation"

11.35-11.55 C. Prestipino “In situ studies of Fe zeolite upon template removal, activation and reaction with NO and N2O by XAS”

Premiazione Giovani e chiusura del convegno

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Contributi orali su Invito

Sessione pre-congresso “Synchrotron Radiation and Earth

Sciences”

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Radiazione di sincrotrone: una sonda per la materia in condizioni estreme

Andrea Di Cicco

Dipartimento di Fisica, Università di Camerino (I)

Il forte sviluppo delle sorgenti di radiazione di sincrotrone ha consentito, in tempi recenti, l'applicazione di tecniche avanzate per lo studio di materia in condizioni estreme. Le proprieta' generali della radiazione di sincrotrone saranno discusse in relazione all'importanza dell'utilizzo per lo studio della struttura microscopica dei materiali. Sviluppi recenti relativi a misure di assorbimento e diffrazione di raggi X ad altissime pressioni e temperature saranno discussi in dettaglio mettendo in evidenza anche la loro importanza nelle scienze della terra.

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Cu, Cd, Hg and Cu-, Cd-, Hg-cysteine treated montmorillonite and vermiculite crystals: an EXAFS study

M.F.Brigatti 1, D.Malferrari 1, L. Medici2, L.Poppi3.

1Dipartimento di Scienze della Terra, Università di Modena e ReggioEmilia (I).

(brigatti@unimore.it;dmalf@unimore.it; lpoppi@unimore.it) 2IMAA - CNR, Area della Ricerca diPotenza - Tito Scalo, Potenza (I).

(medici@imaa.cnr.it) Chemical analyses, thermal analyses combined with evolved gas massspectrometry and powder extended X-ray absorption fine structure (EXAFS)spectroscopy were combined to investigate the mechanism of Cu, Cd, Hg and Cu-, Cd-, Hg-cysteine organometallic complexes adsorbed bymontmorillonite and vermiculite. Obtained results indicate that, at the edge sites of montmorillonite andvermiculite, heavy metals not complexed with amino acids form dimers or acombination of monomers and dimers which are linked by hydroxyl groups or oxygen atomsat the mineral surface. Cu adsorbed on the permanent charged sites ofmontmorillonite develops an outer sphere complex, where the metal issurrounded by a shell of at least one layer of water molecules. Hg and Cd are mostly adsorbed in smectiteinterlayer. There are evidences that Hg is sorbed both as cation complexedto water molecules and as oxides; this behavior should be related to thenarrow range of stability of Hg(II) in water solution following to pH variations. EXAFS analysis carried out on metal and cysteine exchanged mineralsprovided qualitative evidence that: i) nitrogen and oxygen occupies thefirst coordination shell of Cu-cysteine treated minerals; data refinement suggests that the adsorbed copper-cysteine complexes are similar toBis(S-methyl-L-cysteinato)copper(II) organometallic complex. ii) InHg-cysteine treated minerals the same structural position is occupied byoxygen and sulfur atoms; adsorbed complexes arestructurally similar to methyl-L-cysteinato-Hg(II) monohydrateorganometallic complex; bonds at about 2.7 Å in the second shell of coordination of Hg in montmorillonite samples,support that not only thiol but also disulfide/disulfane functional groupmay play an important role in complexation of the heavy metal. iii) Cd-cysteinecomplexes could not be well characterized. Never less EXAFS refinement bothon montmorillonite and vermiculite indicates that sulfur occupies the firstcoordination sphere of Cd and there is a partial agreement with the structure of HgS.

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Water in silicate glasses and melts of environmental interest: from volcanoes to cathedrals.

Francois Farges

Swiss Light Source Institut, Paul Scherrer/ETH Zürich (CH)

farges@univ-mlv.fr

Water reacts with silicate glasses and melts through two main processes: dissolution and percolation. Dissolution of water occurs in melts at elevated temperatures and pressures (so-called "hydrothermal" conditions). In contrast, water interacts with the glass surface at ambiant temperatures and pressures and weathers glasses. We will examine both systems thanks to X-ray absorption fine structure information of in-situ high pressure/high temperature melts and the use of medieval glasses as an analog of a glass exposed to long term atmospheric and microbial weathering. Understanding the structure and properties of molten silicates under in-situ conditions of temperature and pressure is important to model magmatic chambers prior volcanic eruptions. In-situ (high T/P) experiments around a variety of cations (such as Fe, Ni or U) show that geochemical melts have distinct structural properties as compared to their degassed counterparts found on the surface (“lavas”). Of particular interest, is the influence of so-called volatiles and particularly water, which change dramatically the melt properties during magmatic ascension from the deeper crust to the volcanic cones. In-situ macroscopic properties measurement also suggests that hydrous melts, when exposed to high pressures and temperatures, are possibly a type of emulsion, which is violently destabilized during an eruption. Closer to the surface, water is exsolved and mostly released to the atmosphere which contributes to moisture and rainfalls. These two forms of water also affect the durability of natural glasses, which ageing can be compared to modern glasses (for municipal wastes for instance) and to medieval glasses, which show a moderate level of exposure to atmospheric agents but also air pollution in urban areas. Examination of medieval glasses from a variety of cathedrals in northern Europe help to understand how the surface reacts with atmospheric and biogenic agents. For instance, the speciation of sodium on the glass surface is a good tracer of the surface ageing, while manganese redox states probes fairly accurately the amounts of solar (UV) coloration and bacterial activity on their surface (and consequently influence the glass windows durability).

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Applicazioni della spettroscopia d’assorbimento dei raggi x da radiazione di sincrotrone nella mineralogia

applicata al recupero ambientale

Annibale Mottana

Dip. di Scienze Geologiche - Universita’ di Roma Tre Il nome “Molecular Geochemistry” indica, soprattutto negli USA, la disciplina scientifica “that seeks to study chemical reactions at the molecular level through the application of a variety of spectroscopic and microscopic methods” (O’Day, 1999). Questo tipo di ricerca fa uso soprattutto di metodi di due tipi: microscopici e spettroscopici e, tra questi ultimi, della spettroscopia d’assorbimento dei raggi X (XAS) presenti nella radiazione di sincrotrone, per rilevare nel terreno gli elementi chimici minori ed in traccia di rilevanza ambientale. Il nome però è mal scelto: tenta di camuffare sotto un termine alla moda una serie di realtà che vanno viste in modo diverso, se si vuole operare in un modo scientificamente rigoroso. Infatti: a) la maggior parte dei materiali naturali sono aggregati di minerali, con una parte liquida e gassosa che è generalmente piuttosto piccola; b) la spettroscopia, che è scelta come metodologia preferita nello studio dei suoli (o più genericamente dei materiali sciolti di superficie), si deve avvalere della sua ben nota proprietà generale d’essere specifica; c) la XAS è specifica per ciascun elemento chimico; d) per i suoli, uno studio che sia solo spettroscopico mostra severe limitazioni proprio per la sua specificità basata sul componente (elemento chimico) e non sulla fase (minerale); f) quando si afferma che la XAS fornisce informazioni “molecolari” si dice il vero dal punto di vista delle potenzialità teoriche del metodo, ma si formula un’aberrazione scientifica nei casi reali, poiché lo scopo perseguito è, di fatto, solo quello di stabilire lo stato d’ossidazione e la distanza di legame locale dell’elemento chimico sottoposto ad analisi; g) i materiali presenti nei suoli non hanno quasi mai un legame molecolare, ma ionico o covalente o misto: non sono molecole, ma strutture a lungo raggio; gli stessi composti organici dei suoli hanno forze di legame, in genere, miste. C’è, però un punto in cui vi è convergenza tra geochimica e spettroscopia mineralogica: la geochimica ambientale deve necessariamente basarsi su metodi che permettono l’esame di processi che avvengono alla presenza di fase liquida (acqua), poiché l’acqua è il mezzo di trasporto primario dei contaminanti ambientali. La spettroscopia può operare in presenza d’acqua, grazie allo sviluppo di celle opportune, anche rivelando reazioni che avvengono in tempi ristrettissimi (misure risolte in tempo). Quindi tra spettroscopia mineralogica sui composti modello e geochimica ambientale si stabilisce un ponte che dimostra come nelle Scienze della Terra non esistano divisioni, ma graduazioni continue. In questa mia presentazione lascerò da parte il nome alla moda e parlerò di XAS applicata alla Mineralogia ambientale, mostrando così di voler evidenziare le informazioni che la XAS dà sui vari materiali solidi presenti nel miscuglio naturale in esame: privilegerò, cioè, lo “scheletro”, a danno delle altre fasi del suolo. Il maggiore significato attuale degli studi spettroscopici, per le scienze ambientali, va ricercato negli studi non sul suolo in genere, ma piuttosto sul suolo contaminato. Identificare le diverse forme chimiche che presentano in natura certi elementi metallici che possono essere tossici oppure no è di fondamentale importanza ai fini della

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determinazione del rischio chimico creato dalla loro presenza nello strato di superficie del terreno, intendendo con ciò in particolare i suoli, sottili o spessi, che rappresentano luoghi d’accumulo e d’elaborazione dei metalli suddetti in un ambiente potenzialmente reattivo (presenza di acidi, anche se deboli come quelli umici) e di una reattività di lunga durata. Da questi suoli, in tempi diversi, ma sostanzialmente dipendenti dall’evoluzione dei movimenti della falda acquifera e dall’evaporazione, i metalli pesanti, originariamente anche inerti, ma resi mobili dall’interazione con gli acidi, possono diffondersi su larghe aree o per il ruscellamento superficiale oppure per una migrazione della falda d’acqua a diversi livelli di profondità. Sono, quindi, le discariche minerarie, oltre che gli impianti dove avviene il trattamento metallurgico, che presentano i maggiori problemi ambientali studiabili tramite XAFS. Infatti, è attorno a loro che venti ed acque sollevano e distribuiscono elementi chimici inquinanti, sia quegli stessi, utili (es. Pb, Zn, Ag, Fe, ecc) che sono estratti dalla miniera, ma che sempre rimangono in minima quantità nelle discariche e nelle scorie di laveria, sia gli elementi minori non utili presenti nelle ganghe e non per questo meno inquinanti quando entrano in soluzione (es. As, Cd, Cu, Hg, Tl, ecc.). Come casi estremi tra due casi di inquinamento ambientale meglio studiati, in cui la XAS ha dimostrato tutte le sue potenzialità si posssono citare: • quello dei mine wastes, che include i siti per discariche di scorie nucleari; • quello dei suoli contaminati da Pb e Zn. Un test case può essere dato dalla Tolfa, complesso ipoabissale vulcanico acido d’età pleistocenica (provincia magmatica toscana) che è notissimo per i suoi giacimenti di alunite, ma che ha avuto una storia mineraria lunga e variegata. Il suo territorio è ricco, infatti, di piccoli giacimenti di solfuri misti (galena, sfalerite, pirite, cinabro, ecc.) in ganga quarzosa, che sono stati sfruttati prima dagli Etruschi e poi dal 1560 all’inizio del ‘900 e durante le due guerre mondiali. Alla Tolfa il minerale inquinante è il solfuro (di Pb, Zn, Fe e Hg) che, accumulato nella discarica – anche se in piccola quantità – o come residuo d’estrazione oppure come resto del processo d’arricchimento, libera i metalli contenuti e li diffonde per effetto soprattutto della sua interazione con le acque, rese acidissime dal loro attacco sul solfuro stesso. Adottando come base scientifica di partenza il “surface complexation model” (SCM) che prevede l’interazione tra acqua e superficie insatura dei minerali e che sviluppa tridimensionalmente all’interno il processo di trasformazione indotto dalle reazioni di superficie, ed utilizzando lo XANES, che può essere modellato tramite MXAN a chiarire la speciazione sia superficiale sia interna del metallo inquinante, quindi l’eventuale sua sequestrazione nella struttura dei minerali delle argille, stiamo cercando di individuare sinks adatti alla beneficiazione dei suoli della Tolfa. Di qui il passo alla generalizzazione del processo, anche se non breve, sarà possibile. Concludo: rinnovo l’invito a interessarsi a questa applicazione della XAS, che è foriera di sviluppo perché in pieno sviluppo è lo studio dell’Ambiente coi suoi problemi, e segnalo che questo campo di studi non è ora né sarà mai di secondo ordine, dal punto di vista scientifico: anzi, costringerà sempre a mantenersi alla frontiera più avanzata della ricerca perché la Natura, l’Ambiente, pongono problemi assolutamente complessi, per la soluzione dei quali occorrono ricercatori sempre capaci e innovativi.

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Equations of state and field of stability of minerals by high pressure synchrotron radiation powder diffraction

Alessandro Pavese

Dipartimento di Scienze della Terra Università degli Studi di Milano

alessandro.pavese@unimi.it In-situ HP and HPHT powder diffraction investigations have significantly grown in importance in the last score of years for Geosciences at large, and for Mineralogy in particular [Hazen and Finger (1982); Hemley (1998); Hazen and Downs (2000)]. Mineralogy, in turn, often faces HP and HPHT problems which, because of the complexity of the phases involved, lend well themselves to a multidisciplinary approach. The possibility to couple (1) experimental stations at large facilities, allowing collection of a great deal of data on a reasonably short time scale, with (2) more and more versatile conditioning devices, enabling the exploration of a wide P-T range, are the key developments that have boosted the interest in HP and HPHT studies of mineral phases. Powder diffraction investigations at HP and HPHT have remarkably benefited from Synchrotron Radiation Facilities, which provide (i) high brilliance, allowing one to use small amount of sample and to achieve an extremely high pressure (Hemley et al, 1997), (ii) tunability of the incident radiation, to minimise absorption effects due to the HP devices, (iii) focussing of the incident beam, which implies small volumes involved in scattering thereby reducing the effect of the environmental anisotropy (cross section of the beam on the target from 10X10 to 70X70 µm2), and allows high resolution upon a wide pressure interval. Many devices have been designed to achieve HP and HPHT conditions in powder diffraction experiments (Fei and Wang, 2000): among them [1] the membrane Diamond Anvil Cell (DAC) provides a very versatile geometry, largely used for exploration of the high pressure regime, [2] the Large Volume Cell (LVC) represents a compromise between relatively high pressure (P<10 GPa) and extended temperature ranges, [3] the High Temperature DAC (HT-DAC), which makes accessible a large P-T interval, up to about 1300 K and 40 GPa. The use of powdered materials (i) allows one to exploit treatment techniques such as the Rietveld method and the full profile fitting technique of Le Bail et al (1988), and (ii) remarkably speeds up the data collections. This enables to perform dense sampling in P, or P-T, and makes it possible to attain a wealth of data in a relatively short time, and with simple experimental geometries. A dense sampling in P, or P-T, represents a very effective way to reduce the effects of noise and statistical oscillations, which commonly affect the results attained from high pressure powder diffraction and are a serious hindrance when precision is needed, for discrimination between models or determination of relative stability between phases, for instance. One of the most appealing aspects in HP studies for Earth Sciences consists in the possibility to investigate Equations of State of minerals. The reason why of such interest is that the Gibbs energy of a phase at given (P,T) conditions can be expressed by two path integrals, one from (Pr,Tr) to (Pr,T) [isobar], and the other from (Pr,T) to (P,T) [isotherm], where Pr and Tr are pressure and temperature of reference. This latter integration provides a significant energetic contribution to the Gibbs energy, and is related to P-V-T Equations of State, via the expression beneath

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∫T,Pr

T,P

V(P’,T )dP’.

Many hindrances still remain in determining reliable EoSs. Some are of experimental nature (non-hydrostaticity and P-measurement, angular resolution, etc), other due to modelling (EoS expansions). Most efforts are presently steered to tackling such difficulties, in order to allow achievement of experimental conditions providing a HP environment as close to thermodynamic equilibrium as possible. References Fei Y, Wang Y (2000) High pressure and high temperature powder diffraction. Rev Mineral Geochem 41:521-557 Hemley RJ (1998) Ultrahigh-pressure mineralogy. MSA Rev Mineral 37. Hemley RJ, Mao H, Shen G, Badr J, Gillet P, Hanfland M, Hausermann D (1997) X-ray imaging of stress of diamond, iron and tungsten at megabar pressure. Science, 276, 1242-1245. Hazen RM and Down RT (2000) High temperature and high pressure crystal chemistry Rev Mineral Geochem 41:445-519 Hazen RM and Finger LW (1982) Comparative Crystal Chemistry. John Wiley and Sons, New York Le Bail, A., Duroy, H., Fourquet, J.L. (1988): Ab-initio structure determination of LiSbWO6 by X-ray powder diffraction. Mat. Res. Bull., 23, 447-452.

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Structure and Dynamics of Silicate Liquids at High Pressure

Brent Poe1, Claudia Romano2, Hidenori Terasaki3, Christian Liebske3, David C. Rubie3, Ken-ichi Funakoshi4, Akio Suzuki4 and Eiji Ohtani 4

1Dipartimento di Scienze della Terra, Universita’ degli Studi “G. D’Annunzio” – Chieti

1Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 1, Roma 2Dipartimento di Scienze Geologiche, Universita’ degli Studi di Roma Tre

3Bayerisches Geoinstitut, Universitaet Bayreuth, Bayreuth Germany 4Spring-8 Synchrotron Radiation Facility, JASRI, Hyogo, Japan

5Department of Earth Sciences, Tokohu University, Tohoku, Japan The behaviour of silicate liquids at elevated pressure is complex due to the lack of long-range structural order. While silicate melt structure is not completely random, even the classic notion of a tetrahedral anionic framework with cations filling its voids begins to breakdown with increasing pressure. Like crystalline silicates, network-forming cations like Si4+ and Al3+ can undergo pressure-induced coordination increases. However, a number of other compression mechanisms are also possible and that which operates appears to be very dependent upon chemical composition. For example, the absence of non-bridging oxygen (NBO) species in SiO2 prevents the formation of either five- or six-coordinated Si, even at pressures on the order of 100 kbar. Still, its structure is compacted through a narrowing of intertetrahedral Si-O-Si angles. A depolymerizing agent, such as Na2O, creates NBO that are able to increase the coordination of neighboring tetrahedral cations. For aluminosilicate liquids, increasing pressure can lead to changing oxygen coordination via the formation of triclusters, which are oxygen species coordinated to three tetrahedral cations. A variety of spectroscopic techniques, applied mainly to quenched materials, has enabled us to better understand how melt structure changes at high pressure and how these changes can affect their properties. Severely lacking from this picture is the influence of volatiles on both structure and dynamics. The use of high-pressure apparatus combined with synchrotron radiation has enabled us to investigate hydrous silicate melts at conditions where devolatilization does not occur. In this study, we have carried out in-situ falling-sphere viscometry on NaAlSi3O8 liquid as a function of up to about 3 wt% added dissolved water at 2.5 GPa and temperatures to 1550°C. The method allows us to extend the lower viscosity limit (i.e. extend high-T limit and extend compositional range) via real-time monitoring of a sphere’s descent through the liquid as a function of time using shadow radiography. Our results show that, for all samples, viscosity decreases as a function of pressure between 1 atm and 2.5 GPa at 1550°C, indicating that the pressure anomaly can still be observed as depolymerization of the melt increases from nominally zero (dry albite liquid) to NBO/T=0.8 (assuming water speciation entirely as hydroxyl groups at experimental conditions). Also intriguing is the observation that the magnitude of the decrease in viscosity over this pressure interval does not appear to be dependent on the amount of water in the melt (i.e. NBO/T). Examination of molar volumes in this system with respect to e.g. anhydrous alkali silicates might provide an explanation.

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Contributi Orali

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Debye function analysis of synchrotron XRD data: stacking faults and microstrains in spherical palladium crystallites

A. Balerna1, A. Longo2, A. Martorana 3, A. Prestianni3

1 INFN-LNF, via Enrico Fermi, 44, 00044 Frascati, Italy

2 ISMN-CNR, Sezione di Palermo, via Ugo La Malfa, 153, 90146 Palermo, Italy 3 Dipartimento di Chimica Inorganica e Analitica "Stanislao Cannizzaro",

Università di Palermo, viale delle Scienze, 90128 Palermo, Italy-(cric2@unipa.it)

The Debye function approach is used for the simulation of the powder pattern of nanostructured fcc metals with spherical shape. The possibility of structural disorder is taken into account. In particular, for stacking faults reference is made to the statistical treatment of Warren, specifically developed for fcc metals and allowing for twin and deformation stacking faults. Also the effect of microstrains is considered, introducing in the structural model a distribution accounting for the uncertainty in the relative position of couples of atomic centers. The width of the distribution is assumed to be a linear function of the distance between scatterers. It is also demonstrated that this approach is consistent with the Warren-Averbach procedure for size-strain determination. An example of fitting of the simulated intensity to the XRD pattern of Pd supported on pumice recorded at the BM08 beamline of ESRF is given.

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Photoelectron-Auger coincidence study of Sn/Ge(111): role of the magnetic sublevels discrimination

F. Da Pieve1, R.Gotter2, G.Stefani1, A.Ruocco1, F.Offi1, A.Morgante2, H.Yao3 and

R.A.Bartynski3.

1Dept. of Physics and Unita’ INFM, University of Roma Tre, Rome (I). (dapieve@fis.uniroma3.it)

2National Laboratory TASC-INFM, Trieste (I). 3Dept. of Physics and Astronomy and Laboratory of Surface Modification,

Rutgers University, Piscataway, New Jersey (USA) . . The recently highlighted selectivity on magnetic sublevels of AR-APECS (Angular Resolved – Auger Photoelectron Spectroscopy) is proposed for the study of nanostructured magnetic materials. The novel possibility to experimentally quantify the contribution of the m sublevels to the LMDAD signal, or, by means of the chirality preserved by the coincident photoelectron, to measure linear magnetic dichroism in the Auger emission, where the valence electron are directly probed by the Coulomb interaction, will be presented. Furthermore, this magnetic-like discrimination, joined with the already known APECS selectivity, in terms of the extreme surface sensitivity or the capability to disentangle non equivalent atomic site of the same chemical specie, make AR-APECS suitable for resolving complex systems where long range order is not enough to be probed by diffraction techniques and short range local order is too manifold to be probed by XAS near And Extended structures. In the past twenty years, a steadily increasing number of electron-electron coincidence experiments on atoms and molecules have demonstrated the capability of investigating complicated systems with sensitivity and specificity well beyond the limits imposed by conventional electron spectroscopies. Over the past decade or so, Auger-photoelectron coincidence spectroscopy (APECS) has emerged as a powerful technique for obtaining detailed information about complex materials systems. Moreover, the recent advent of angle resolved (AR-APECS) has introduced a new level of discrimination in studying the distribution of electrons photoemitted from complex systems. A series of recent results on 1/3 ML (3x3) Sn/Ge(111) have drawn attention on the possibility of selecting specific magnetic sublevels of both Auger and photoelectron wavefunctions. Good use of this capability has been made in singling out otherwise overlapping components of Sn M5N45N45 multiplet split Auger spectra, thus demonstrating that resolution in angle improves discrimnation in the energy scale as well. It will be discussed the possibility that AR-APECS will produce a new stream of experiments with unprecented discrimination in the magnetic sublevels of the intermediate core hole. This spectroscopy bears the potential of disentangling information about complex systems that are hidden to conventional electron spectroscopies.

22

Variable photon energy PES of M(BH4)4, M = Zr, Hf, U: study of the role of f orbitals in chemical bonding

Monica de Simone1, Marcello Coreno2, Jennifer C. Green3, Aled Jones3, Sean

McGrady3, Helen Pritchard4

1Laboratorio TASC-INFM, Area Science Park, I-34012 Basovizza, Trieste, Italy

2CNR-IMIP, Montelibretti, I-00016Roma, Italy 3Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK

4Chemistry Department, Kings College, The Strand, London, WC2R 2LS, UK Though the capacity of s, p and d orbitals to form covalent bonds in inorganic molecules is well documented, the role of f orbitals in bonding is more controversial. In lanthanide and actinide complexes the energies of the f orbitals place them in the valence region but their radial distribution as a consequence of their low principal quantum number is core-like and their high angular momentum bequeaths nodal properties which can lead to low overlap with ligand orbitals. One of the most direct experimental methods of studying the atomic orbital (AO) composition of molecular orbitals (MOs) is variable photon energy photoelectron (PE) spectroscopy. The photoionisation cross section (PICS) of a PE band shows features which may be attributed to the AOs from which the originating MO is composed. For example the closeness of a PICS maximum to threshold is a function of the angular momentum of the AO, d and f orbitals exhibiting delayed maxima. Also AO with radial nodes show Cooper minima which is useful in distinguishing s and p bands of principal quantum number > 1 or 2 respectively. Most dramatically d and f ionisations may be significantly enhanced by a resonant process, whereby an inner shell p or d electron undergoes an excitation into a vacant orbital of d or p character followed by a super Coster-Kronig decay, resulting in the ejection of a bound d or f electron. The photon energy at which these various features occur is predictable to within a few eV so the overall PICS profile may be analysed productively. In ideal circumstances a quantitative model of key MO may be constructed. The series of volatile tetrahedral molecules M(BH4)4 where M = Zr, Hf and U, offers a unique opportunity to undertake a comparative bonding study. In Td symmetry the ligand symmetry adapted linear combinations (SALCs) span the representations a1, e, t2 and t1. Only an f-orbital can provide a symmetry match for the t1 combination. Previous DFT calculations suggest that as a consequence the 1t1 orbital is the HOMO for Zr, and Hf but the HOMO-1 for U. One aim of the current study was to detect this f-orbital covalency

23

Electronic and vibronic structure of copper-phthalocyanine: a gas phase and molecular solid study

F. Evangelista1, A. Ruocco1, S. Stranges2, M. Alagia3, G. Stefani1.

1Dipartimento di Fisica, Universita’ di Roma Tre (I)

(evangelista@fis.uniroma3.it) 2Dipartimento di Chimica, Universitá di Roma "La Sapienza" (I)

3INFM-TASC, Trieste (I) In the study of organic-inorganic interfaces an exhaustive knowledge of the electronic structure of the isolated molecule may represent an important basis for the interpretation of interface properties. In fact one of the open questions in this field is the intimate nature of the molecule-substrate bonding and the relation between this interaction and the growth morphology of molecular films. In this work we present a gas phase study of the copper-phthalocyanine organic molecule. We performed a high resolution photoemission and photo-absorption experiment and we compared these results with those obtained in the molecular solid phase. The shown gas phase ultraviolet photoelectron spectra manage to disentangle several electronic states of the molecule below the Fermi level and agreement with the theory is discussed [1]. A detailed study of the HOMO level is presented. In particular the high energy resolution available on the GAS PHASE beamline allowed to resolve a feature already observed [2], but here clearly distinguishable for the first time: we assign it to the vibrational C-C stretching. No C-H stretching was observed, thus suggesting a localization of the HOMO level in the porphyrazinic ring. Regarding the C-H stretching a polarization dependent XPS study from C 1s core level has been performed on CuPc films of different thicknesses deposited on a gold substrate. The behaviour of a component claimed to be a vibrational coupling with the photoexcitation of aromatic carbon atoms [3] is discussed. [1] Liao Meng-Sheng, Scheiner S., J. Chem. Phys.,114 (2001) 9780 [2] Kera S., Yamane H., Sakuragi I., Okudaira K. K., Ueno N., Chem. Phys. Lett. 364 (2002) 93 [3] Papageorgiou N., Ferro Y. Salomon E., Allouche A., Layet J. M., Giovanelli L., Le Lay G., Phys. Rev. B, 68 (2003) 235105.

24

X-ray absorption studies of the local environment of zinc ions bound to the bacterial photosynthetic reaction center

L. Giachini1,2, F. Francia2, A. Mallardi 3, G. Palazzo4 , E. Carpenè5,

G. Venturoli1,3 F. Boscherini1,2.

1INFM e 2Dipartimento di Fisica, Università di Bologna (lisa.giachini@bo.infm.it) 2 Dipartimento di Biologia, Università di Bologna. 3 Istituto per i Processi Chimico-Fisici, CNR, Bari.

4 Dipartimento di Chimica, Università di Bari. 5Dipartimento di Biochimica ‘G. Moruzzi’, Università di Bologna.

Binding of transition metal ions to the reaction center (RC) protein of the photosynthetic bacterium Rhodobacter sphaeroides slows the light-induced electron and proton transfer to the secondary quinone, QB (Utschig et al., 1998, Biochemistry 37, 8278; Paddock et al., 1999, Proc. Natl. Acad. USA 96, 6183). On the basis of X-ray diffraction (XRD) at 2.5 Å resolution a site has been identified at the protein surface which binds Cd(II) or Zn(II). Both metal ions bind to the same cluster formed by AspH124, HisH126 and HisH128. A water molecule was also proposed to interact with the Zn (Axelrod et al., 2000, Proc. Natl. Acad. Sci. USA 97, 1542). Recent data suggest that inhibition of proton transfer by Cd(II) is predominantly a consequence of competition with protons for binding to HisH126 and HisH128, thus hampering the function of these residues as proton donor/acceptors along the proton pathway to the QB site (Paddock et al., Biochemistry 42,9626, 2003). Determination of the local structure of the bound metal ions is expected to contribute significantly to elucidate the details of the inhibition mechanism. For this reason we performed Zn K-edge X-ray absorption measurements at the GILDA beamline of the ESRF on Zn-doped RCs embedded into polyvinyl alcohol films at both room and liquid nitrogen temperature. Data analysis has been performed using ab-initio simulations and multiparameter fitting; structural contributions up to the fourth coordination shell and multiple scattering paths (involving three atoms) of significant amplitude have been included. Results for complexes characterized by a Zn to RC stoichiometry close to 1 indicate that Zn binds two O and two N atoms in the first coordination shell. The two N atoms come from His, and only one of the two O atoms comes from an amino acid (Asp or Glu); the second O atom belongs to a water molecule. Complexes characterized by approximately 2 Zn ions per RC show a second structurally distinct binding site, involving three N and one O atom, all coming from non-aromatic residues. The results obtained for the higher affinity site nicely fit the coordination proposed on the basis of XRD data. The second binding site, revealed by our investigation on non-crystalline samples, is most probably located in a more disordered domain of the RC protein and might have a hitherto not appreciated role in charge transfer inhibition.

25

Effect of the oxygen fugacity on V structural role in synthetic basaltic glasses: a XAS study at the V, Ti, and Fe K-edge

Gabriele Giuli1, Eleonora Paris1, Jim Mungall2

1Dip. Scienze della Terra and INFM, Universita' di Camerino, Italy; (gabriele.giuli@unicam.it)

2Dept of Geology, University of Toronto, Canada. In this study we present structural data on Vanadium in silicate glasses of basaltic composition. Previous work has been done to determine the influence of bulk glass composition and V-content on the V structural environment in the glasses (Giuli et al., 2004). In this work we investigated the effect of oxygen fugacity (from air down to iron-wustite IW buffer) on the V environment. XAS spectroscopy has been used to investigate V coordination number, oxidation state and V-O distances in the glasses. The spectra have been collected at the GILDA beamline of the ESRF storage ring (F) using a Si(3 1 1) monochromator to obtain high resolution spectra. Comparison of the spectral features of the investigated glasses with those of reference materials allows to evidence that, while [4]V5+ and [5]V5+ are the predominant form of Vanadium in the glasses synthesised in air, V progressively reduces to [5]V4+ and [6]V3+ at QFM and IW buffers respectively. Combined studies at the Ti and Fe K-edge on the same samples allowed to evidence that, while Ti environment does not change with oxygen fugacity, Fe structural role varies from [4]Fe3+, for the glasses synthesised in air, to [5]Fe2+ for the most reduced glasses. These data clearly evidence a strong variation of the V and Fe structural role in the basaltic magma according to the oxygen fugacity. Moreover, the data on the oxidised glasses suggest an interaction between V and Fe possibly resulting from competition to enter the tetrahedral network. References cited: Giuli G., Paris E., Mungall J., Romano C., Dingwell D. (2004) V oxidation state and coordination number in synthetic silicate glasses by XAS. Am. Min. (accepted).

26

A novel configuration for multi-coincidence technique and its application to double photoionization in solids

R.Gotter1, F.Offi3, J.Berakdar2, A.Ruocco3, F.Da Pieve3 and G.Stefani3

1National Laboratory TASC-INFM, Trieste (I). (gotter@tasc.infm.it)

2 Max-Plank-Institut für Mikrostrukturphysik, Halle (D). 3Dept. of Physics and Unita’ INFM, University Roma Tre, Rome (I).

A novel approach for multi-coincidence technique on solids has been tested at the ALOISA end station of the ELETTRA synchrotron radiation source. It consists of time coincidence detection between a frame of hemispherical analysers and a channeltron used as a time of flight (TOF) spectrometer. This configuration presents the relevant advantage to be multichannel in energy, thus producing a sizeable increase in the phase space volume sampled by the electron-electron coincidence experiment. The present approach has been used to perform a survey for double photoionization (DPI) events on the Cu(111) single crystal surface, which is characterised by an expected cross section 104 times smaller than the “single” photoionization one. The expected DPI cross-section, computed prior to the experiment, has constituted guidance in selecting experimental conditions. Compared to the only previous DPI experiment, in this case a higher photon energy (hν=150 eV) has been used. The reported experiment is of a great physical relevance as it constitutes a test of recently developed descriptions of DPI in solids, and more generally it establishes a relevant step-forward in the description of electron correlation in solids. Our results, although limited in breath by the insufficient time discrimination of the present TOF spectrometer, clearly show that two main channels of similar relevance contribute to the total coincidence counts, that is, the resonant Auger-photoelectron and the non-resonant DPI. This evidences the presence of a sizeable amount of double photoionization events, a fact that may open the possibility to directly explore the electron correlation, once a better time-discriminating TOF spectrometer is implemented.

27

Structural study of 1,4-cyclohexadiene adsorption on Si(001) surface by low energy photoelectron diffraction

R. Gunnella1,3 ,M. Shimomura2 , M. Munakata2 , T. Takano2,

T. Yamazaki2 , T. Abukawa2 and S. Kono2

1 Udr INFM ,Dip.to di Fisica Università di Camerino, Italy 2 Institute of Multidisciplinary Research for Advanced Materials , Tohoku University, Sendai 980-8577

Japan 3 LNF-INFN , CP 00013 Frascati (Italy)

The structural properties of the sub-saturation coverage of 1,4-cyclohexadiene (C6H8) on single domain Si(001)-2x1 surface have been investigated by using photoelectron diffraction (PD) at the C1s core level and at the photon energy of 330eV. The high resolution core level study allows to determine the presence of a shifted replica of +0.9 eV in kinetic energy. The structural properties of adsorbed molecules are discussed at the light of ab-initio multiple scattering calculations on several adsorption models with about the same least total energy. This quantitative experimental determination timely follows the many qualitative assessments present in literature for this important prototypical case of functional Si substrate and aims to fill the gaps between several experiments reported.

28

Photoelectron angular distribution by resonant Auger decay of core_excited H2O: experiment and theory

I. Hjelte 1, A. De Fanis2,3, V. Carravetta4, N. Saito5, M. Kitajima 6, H. Tanaka6, H. Yoshida7, A. Hiraya7, I. Koyano8, L. Karlsson1, S. Svensson1, K. Ueda2 and M.N.

Piancastelli1,9.

1Department of Physics, Uppsala University, Sweden 2Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Japan

3Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo, Japan 4IPCF-CNR, Pisa, Italy

5National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan 6Department of Physics, Sophia University, Tokyo, Japan

7 Department of Physical Science, Hiroshima University,, Japan 8Department of Material Science, Himeji Institute of Technology, Japan

9Department of Chemical Sciences, University ‘Tor Vergata’, Italy We have obtained vibrationally resolved spectra for the lowest-lying final states reached after participator resonant Auger decay of core-excited water. The first four resolved single vibrational components of the X-state in the photon energy regions including the O 1s->4a1 and the O 1s->2b2 core excitations show, in particular, an unusually large relative spread in β values across both resonances, that the available model for the angular dependence of normal Auger decay fails to describe. The photoabsorption spectrum, the electron decay spectrum and the β parameter have been calculated by a one-step theoretical model, based on the scattering K-matrix, including two vibronic resonant states. The results of the numerical simulation show qualitative agreement with the trends detected in the experimental values and explain the strong energy dependence of β for photon energies around the core excitations as an effect of both vibrational/lifetime interference and coupling between direct and resonant photoemission pathts by interaction terms of different sign for different final vibrational states.

29

The early hydratation of Portland cements investigated with synchrotron radiation

X-ray powder diffraction (SR-XRPD)

M. Merlini 1*, G. Artioli 1,T. Cerulli 2

1Dipartimento di Scienze della Terra, Università di Milano (I) *(marco.merlini@unimi.it)

2Mapei S.p.A., Research and Development Lab., Milano (I) Cements and concrete are building materials widespread all over the world. The modern use of chemical admixtures in cements and concrete make essential an accurate knowledge of the hydration process of cement, in particular the "early hydration", that is what happens in the first hours of the process. In fact an accurate prediction of the physical behaviour of the cement with added admixture will be achieved only if the interaction between clinker particles, hydrated phases and inorganic or organic admixtures will be clarified. We performed SR-XRPD on hydrating paste composed by pure clinker phases and Portland cements with added admixtures. Data were collected at the GILDA beamline and BM16 (now ID31) at ESRF. The data were analysed with Rietveld method. The results of both time-resolved (GILDA) and high resolution (BM16) powder diffraction experiments allow a deep insight into the hydration process, which is the sum of several chemical reactions. In particular the cristallographic evolution of ettringite (monitored by change in lattice parameters), the main hydrate phase in the first hours of the cement hydration process, can be related to a SO3/H2O variable ratio in the structure and hence to the effective sulphate availability and diffusion in the systems, an important parameter which can affect the setting time. Time-resolved experiments allowed the monitoring of the dissolution of clinker phases and crystallisation of hydrate phases (fig. 1); their kinetics are clearly influenced by the class of additives employed. The results are quite in agreement with independent ESEM observations and calorimetric measurements and help in giving full details of the cement hydration process. Fig. 1 - Evolution of clinker phases (C3S, C3A) and hydrated ones during the hydration of PC with added superplasticizers.

Time (min)

0 100 200 300 400 500

Weight fraction 0.0

0.1

0.5

0.6

C3S

C3A

ettringite

Ca(OH)2

monosulphate

30

SINBAD and SISSI, the new infrared beamlines at DAΦΦΦΦNE and ELETTRA

A. Nucara,1 A. Marcelli, 2 S. Lupi,1 M. Cestelli Guidi1,2, M. Piccinini,2 P. Calvani1,and E. Burattini 2,3

(calvani@roma1.infn.it)

1INFM and Dipartimento di Fisica, Università “La Sapienza”,Roma, Italy 2Laboratori Nazionali di Frascati - INFN, Via E. Fermi 40, 00044 Frascati, Italy

3Università di Verona, Strada Le Grazie 15, 37138 Verona, Italy

SINBAD, the Synchrotron INfrared Beamline At DAΦNE, the commissioning of which started in 2002, is providing the first results. Its high brilliance has been used, in particular, to perform absorption experiments in diamond anvil cells (DAC) working up to 10 GPa. The window has a typical size of 0.3 mm, a dimension which precludes the use of conventional sources. Thus, by using a DAC we first observed in the far infrared the metallization process induced by pressure in La1-xCaxMnO3 manganites. The radiation transmitted by the DAC, using SINBAD, was at least 20 times more intense than using the mercury internal source of the interferometer. SINBAD also provides unique performances for the far-infrared reflectivity measurements on small crystals. Presently, the beamline is engaged in an effort to first measure both superconducting gaps in suitably doped MgB2, which is available in single crystals of maximum size 0.2x0.2 mm. Meanwhile, the construction of the first infrared beamline on ELETTRA, SISSI, is proceeding as planned. The final assembling of the beamline, which will be mainly devoted to infrared microscopy, will start next summer. The infrared radiation will be delivered to the experimental station at the end of 2004. Preliminary measurements of the infrared emission from a bending magnet of ELETTRA, by using a beamline for diagnostics in the visible range, exhibited both a linear dependence of the intensity from the current in the ring and a good beam stability. SISSI will also profit of the "edge radiation", a new kind of infrared emission that was first observed in Orsay under a collaboration between LURE and Università La Sapienza.[1] [1] Y-L. Mathis, P. Roy, B. Tremblay, A. Nucara, S. Lupi, P. Calvani, and A.Gerschel Phys. Rev. Lett. 80, 1220 (1998).

31

Bulk Sensitive Photoemission: design and first results of a novel high resolution spectrometer

F. Offi1, G. Cautero2, M. Cautero2, A. Fondacaro1, M. Grioni 4, P. Lacovig2, B. Krastanov2, G. Monaco5, G. Paolicelli1, P. Pittana2, M. Sacchi3, G. Stefani1, R.

Tommasini2, P. Torelli5 and G. Panaccione6

1INFM and Dip. Fisica Univ. Roma III, Via della Vasca Navale 84 00146 Roma 2Sincrotrone Trieste s.c.p.a., S.S. 14 Km 163.5 , I-34012 Basovizza – Trieste

3Laboratoire LURE, Centre Universitaire Paris-Sud BP 34, F-91898 Orsay (FR). 4EPFL, Institut de Physique des Nanostructures CH-1015 Lausanne (Switzerland)

5ESRF, 6 rue Jules Horowitz, BP 220, 38043 Grenoble Cedex 9 (France) 6INFM-TASC, S.S. 14 Km 163.5 , I-34012 Basovizza – Trieste (Italy)

In recent years growing interest has been dedicated to photoemission experiments at high energy since a significant bulk sensitivity in photoemission measurements can be achieved only by increasing the kinetic energy of the analysed photoelectrons. Within the 5th European framework, a RTD project named VOLPE (VOLume PhotoEmission from solids) has been funded aiming to develop a new electron spectrometer with the ultimate goal to perform photoemission experiments in the electron kinetic energy range of 6-10 keV with an energy resolution of 20-30 meV. The spectrometer is a hemispherical deflector analyser with electrostatic input lens and two-dimensional position sensitive detector and it will be characterised by an ultimate resolving power of 3·105 at 10 keV. The present performances of the instrument, resulting from the first tests performed at the beamline ID16 of ESRF, are presented. Good statistics spectra as well as an energy resolution comparable to modern surface sensitive photoemission spectra is achievable up to 8 keV of electron kinetic energy. Deep and shallow core level (2p and 3d) signals have been measured from a buried layer roughly 100-120 Angstrom underneath the surface. Valence band spectra, including Fermi Edge profile, measured from polycrystalline Ag, reveal an overall energy resolution (photon source plus analyzer) of about 110-150 meV at 6-8 keV. We remark that the corresponding resolving power of 5*104 is one of the highest values ever achieved in photoemission measurements from solid samples.

32

X-ray absorption spectroscopy in MnxGe(1-x) diluted magnetic semiconductor: experiment and theory

L. Ottaviano1, M. Passacantando1, S. Picozzi1, G. Profeta1, F. Priolo2, and A.

Continenza1.

1Dipartimento di Fisica Univ. dell’Aquila, Via Vetoio 10 I-67010 Coppito-L’Aquila (Italy). (luca.ottaviano@aquila.infn.it)

2 INFM, Dipartimento di Fisica e Astronomia, Università di Catania, I-95123 Catania (Italy) Soft X-ray absorption spectra obtained for ion-implanted MnxGe{1-x} ferromagnetic semiconductors are compared with accurate first-principles calculations. The well defined features in the experimental spectra are recognized as a signature of efficient Mn dilution within the Ge host, as demonstrated by comparing the Mn spectra in diluted MnGe alloys with other Mn-Ge crystalline competing phases. The similarity of the Mn absorption spectrum with other magnetic semiconductors shows that the lineshape is only slightly affected by the nature of the semiconducting host, provided that an effective dilution is achieved. These findings assess the relevance of ion-implantation techniques in the dilute magnetic semiconductors framework.

33

Vibrational properties of nanocrystalline Fe studied by nuclear inelastic scattering

L. Pasquini1, A. Barla2, A.I. Cumakov2, O. Leupold2, E. Bonetti1, A. Deriu3,

R. Rüffer2

1Dipartimento di Fisica, Università di Bologna and INFM (Italy). (luca.pasquini@bo.infm.it)

2ESRF, Grenoble (F). 3Dipartimento di Fisica, Universita' di Parma and INFM (I).

The investigation of vibrational dynamics in low-dimensional and nanostructured solids is a rapidly growing research field, powered by the interest in thermodynamic, conductive, and optical properties of mesoscopic systems [1]. In the vibrational density of states (VDOS, g(E)) of nanocrystalline (NC) materials, both finite-size effects and interface-related phenomena due to the large fraction of disordered interfaces are expected. In this work, nuclear inelastic scattering (NIS) of synchrotron radiation was employed to determine the VDOS in NC Fe samples with different crystallite size d, prepared by gas-phase condensation [2]. NIS experiments were carried out on ID18 at ESRF, with a final bandwidth of 0.6 meV. In NC samples, an enhanced population of low-energy modes and a broadening of the longitudinal peak at about 36 meV was observed [2]. The softening was attributed to oxidation effects and to vibrations of atoms at the crystallite interfaces, with modified local environment and weak force constants. The low-energy VDOS exhibits the Debye-like g(E)=aE2 dependence over the whole range 1.5-15 meV. The broadening of the longitudinal peak was ascribed to damping of phonons in confined geometry. Indeed, the broadening parameter Γ is correlated and consistent with d, varying from 1.1 to 0.5 meV when d passes from 6.6 to 13 nm [2]. The d-dependence of Γ suggesting that phonon lifetime Γ≈ /2hτ and mean free path λ decrease with decreasing d, can be explained assuming a confining action played by disordered interfaces. [1] M.A. Stroscio, M. Dutta, Phonons in Nanostructures, Cambridge University Press, Cambridge, England, (2001) [2] L. Pasquini, A. Barla, A.I. Chumakov, O. Leupold, R. Rüffer, A. Deriu, E. Bonetti, Phys. Rev. B 66, 073410, (2002)

34

NEXAFS study of a Pt-containing rod-like organometallic polymer (Pt-DEBP) depositated onto HOPG, Au/Si(111), Cr/Si(111) and Si(111) surfaces: molecular orientation

G.Polzonetti1, C.Battocchio2, I.Fratoddi 2, F.Borgatti3, M.Pedio3, N.Mahne3,

A.Giglia3, B.Doyle3, S.Nannarone3, M.V.Russo2

1Dept. of Physics and unità INFM, INSTM and CISDiC, University “Roma Tre”, Via della Vasca Navale,

84 - 00146 Rome (Italy) 2Dept. of Chemistry, University "La Sapienza" P.le A.Moro, 5 - 00185, Rome (Italy)

(chiara.battocchio@uniroma1.it) 3TASC-INFM, in Area Science Park, SS 14 Km163, 5, Basovizza - Trieste (Italy)

Polymeric organometallic compounds are of interest for several reasons such as their electronic and optical properties and their applicability as active components in commercial electronic or optoelectronic devices. Among others, poly-yne polymers containing transition metals in the main chain (Pt, Pd) have recently received great attention because of their peculiar physical properties such as third-order non-linearity, photoluminescence and magnetic electronic properties, arising by the delocalized π system involving also the metal orbitals. The poly-yne Pt-DEBP has been tested as sensitive membrane in a surface acoustic wave (SAW) device, giving a quite good response to relative humidity variations. The morphology of the thin film could influence the efficiency of the device; for instance it is believed that orientation of the polymer chains can improve the acoustic phase velocity variations in the SAW gas-sensor. In this framework we have started to investigate the influence of the oriented substrate HOPG and metals often used for the preparation of electronic devices such as Au and Cr. In this work the influence of the substrate on the molecular orientation of the organometallic polymer Pt-DEBP, i.e. [-Pt-(PBu3)2-C≡C-C6H4-C≡C-]n, deposited as thin film on HOPG (highly-oriented-pyrolytic-graphite), Si(111), Au/Si(111) and Cr/Si(111) substrates, has been investigated by near-edge X-ray absorption spectroscopy (NEXAFS). Angular dependent analysis of the π* resonance occurring at 285.50 eV photon energy and deriving by the benzene carbon orbitals show a strong polarisation effect for all substrates, and a preferential molecular orientation at about 50° to the surface normal is observed. The arrangement of the Pt-DEBP chains is governed by the interplay of the intermolecular forces and the polymer-substrate interaction that promote a high degree of molecular order not depending from the substrate orientation, because of the predominant intermolecular interaction.

35

c/a anomalies on cadmium: an X-ray diffraction study

G. Pratesi1, M. Minicucci2, A. Di Cicco3, P. Rocci3

1INFM Unita’ di Camerino

2Centro Grandi Apparecchiature Universita’ di Camerino 3Dipartimento di Fisica Università di Camerino

Although the high pressure behavior of zinc and cadmium hexagonal close packed metals has been intensely studied in the past years, the question on the anomalous compression properties of Zn and Cd is still open. Here we report X-Ray diffraction study on Cadmium at room temperature and high pressure up to 16 GPa in order to obtain the c/a trend as a function of the pressure. We see clearly effects of the non hydrostaticity in the low pressure range, but our data

confirm the anomaly in the volume dependence of the c/a axial ratio.

36

In situ study of Fe zeolite upon template removal, activation and reaction with NO and N2O by XAS

C. Prestipino1, Lamberti1, G. Spoto1, A. Zecchina1,

F. D’Acapito2 and G. Berlier1.

1Department of Inorganic, Physical and Materials Chemistry, University of Torino, Italy. 2GILDA CRG and INFM OGG c/o ESRF.

EXAFS/XANES spectra have been collected at ESRF (BM8 GILDA) under in situ conditions of different Fe-zeolite samples having a sufficient iron dilution (Si/Fe = 90) to be considered a “true” catalysts in partial oxidation reactions (e.g. benzene to phenol). Fe3+ species are incorporated, during zeolite synthesis in framework Si sites, where they exhibit a tetrahedral symmetry being coordinated to four oxygen atoms of the lattice. Template burning in air and sample activation in vacuo causes a progressive migration of ordered iron from framework sites into disordered extraframework (EF) positions. This phenomenon is associated to a reduction from Fe3+ to Fe2+. The structural disorder of EF Fe species is monitored by the striking decrease of the EXAFS signal, while the changes of the oxidation state has been indicated in the XANES part of the X-ray absorption spectra. So obtained EF Fe2+ species are characterized by very high coordinative unsaturation, being able to form Fe2+(NO)3 complexes upon interaction with NO at RT. Interaction with N2O at 523 K causes the overall re-oxidation of iron species resulting in a catalyst containing EF species characterized by a less pronounced coordinative unsaturation. IR spectroscopy and catalytic test support XAS data.

37

Contributi Poster

38

Circular Dichroism in the Angular Distribution of Photoelectrons from Methyl-oxiranes Vapour

M.Alagia1, G.Alberti 2, G.Contini3, P.Decleva4, G. Fronzoni4, T.Prosperi3,

M. Stener4, S.Stranges5, S.Turchini3, N.Zema3

1ISMN-CNR, Roma, Italy 2IMIP-CNR, Roma, Italy 3ISM-CNR, Roma, Italy

4Dip. di Scienze Chimiche, Univ.Trieste, Trieste, Italy 5Dip. Chimica, Univ. Roma1, Roma, Italy

Circular Dichroism in experiments with parity breaking geometries, reveals electronic properties dependence on molecular and atomic dissymmetry which are otherwise embedded in the isotropic spectrum. Natural Circular Dichroism (NCD) is a well-established technique which plays a key role in the determination of the electronic structure of chiral molecules and of their stereochemical properties. Few works are reported in the literature for what concerning the VUV-Soft X-Ray energy range; in particular first asymmetry data in VUV photoemission [i] has been recently performed on vapour phase bromocanphor showing an asymmetry value of the order of 10-2. The angular resolved photoemission spectroscopy (ARPES) is a very promising technique in detecting the chiral properties of molecules. The dichroic effect in photoelectron spectroscopy is due to the dipole interaction term, while the absorption process is related to the second order interference terms, the electric dipole-electric quadrupole and electric dipole-magnetic dipole, the (E1-E2) and (E1-M1) mechanisms. Therefore the Circular Dichroism in Angular Distribution of photoelectrons (CDAD) is expected to be much more intense. We report extended circular dichroism in the angular distribution of photoelectrons of valence spectra for R(+) and S(-) isomers in methyl-oxirane vapour phase. Methyl-oxirane is a chiral building block for several asymmetric synthesis and in the present case is a good test molecule because its conformational rigidity makes it amenable to extensive calculations and to mono-signated dichroic absorption bands. The maximum detected asymmetry of the dichroic parameter D was of the order of 5x10-2. Carful analysis of the electron kinetic energy dependence of the D parameter and comparison to the calculated values are presented.

39

Gas Phase Photoemission Beamline @ Elettra: status of the project

M. Alagia1,2, L. Avaldi3,2, M. Coreno3,2, M. de Simone2, M. Pilosio2 ,

R. Richter4, K.C. Prince4, S. Stranges5,2.

1CNR-ISMN Sez.Roma1, P.le A. Moro 5, I-00185 Roma, Italy 2INFM-TASC, Gas phase beamline@Elettra,Area Science Park, I-34012 Basovizza, Trieste, Italy

3CNR-IMIP, Area della Ricerca di Romai,CP10, I-00016 Monterotondo Scalo, Italy 4Sincrotrone Trieste, Area Science Park, I-34012 Basovizza, Trieste, Italy

5Dipartimento di Chimica, Università di Roma “La Sapienza”, I-00185 Roma, Italy 4The Abdus Salam International Centre for Theoretical Physics, I-34014 Trieste, Italy

The Gas Phase beamline is a joint venture between the Consiglio Nazionale delle Ricerche (CNR), Istituto Nazionale di Fisica della Materia (INFM) and Sincrotrone Trieste and is operated as a Gruppo di Ricerca (GdR) at the synchrotron radiation facility Elettra, Trieste. The beamline, devoted specifically to research in gaseous systems, is fed by an undulator which delivers light in the range from 13.6 eV to above 1000 eV. Activity in instrumentation development in 2003 has been focussed mainly on the design and construction of a multipurpose end-station. The end-station has been designed in order to host most of the instrumentation (detectors, sources, etc.) already available. This will reduce the time spent in assembling/disassembling experiments and optimize the use of beamtime. The dispersed fluorescence spectrometer commissioned in 2003 has been successfully used in several beamtimes. Finally the new grating (140 lines/mm) installed in the year 2002 has been completely commissioned. The results showed good suppression of high-order radiation (a factor 5 and 100 better than the previous grating for the second- and third-order radiation respectively) in the range 15-30 eV, while maintaining an acceptable resolution (resolving power about 6000). The in-house research of the GdR has produced several notable results which will be presented at the meeting. Among them we list the observation of initial state effects in the double photoionization of the ns2 states (n=2-5) of rare gases, the observation by PIFS of Stark effects in the cascade decays of He doubly excited states, the study of the resonant Auger spectrum of Cs at the 4d-6p resonances. Moreover a continuous supersonic jet generating free radicals by the flash pyrolysis method has been successfully operated in the case of the CH3 molecule. C1s absorption features using high photon energy resolution could have been observed as well as ion-coincidence events (e.g. H+/CH2+ channel) in this radical for the first time.

40

New experimental approach to exploit sum rules in x-ray Resonant Raman Scattering

E. Annese1, A. Tagliaferri 2, G. Ghiringhelli2, N. B. Brookes3, L. Braicovich2

1 INFM, Dipartimento di Fisica dell’Universita’ di Modena e Reggio,

Via Campi 213/A 41100 Modena, Italy

2INFM, Dipartimento di Fisica del Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy

3European Synchrotron Radiation Facility, Grenoble, BP 220, France

In the past decade x-ray magnetic circular dichroism (XMCD) has evolved into an important magnetometry tool in the study of transition metal and rare-earths compounds (i.e. multilayers, nanostructure, etc). Recently, it was demonstrated that information on the ground state properties of a magnetic systems can be recovered through sum rules in x-ray Resonant Raman Scattering (RRS) by exploiting a new experimental approach[1]. This gives information that cannot be obtained with x-ray absorption. It consists of measuring the integral of the spectrum along the outgoing energy hνout in a given de-excitation channel[1] as a function of the incident energy hνin, and is called Integrated RRS (IRRS). First applications of the IRRS approach were performed by using as analyser a diode covered by a convenient low pass filter [2][3]. This approach is not useful when the emission from other elements in a compound or in the substrate (for thin film) is close in energy to the chosen channel. A new analyser for measuring IRRS spectrum in the energy range from 500 eV to 1000 eV with a band pass of the order of 50 eV has been developed. The analyser is based on a single spherical multilayer (ML) W/Si coupled with a detector. It has the advantages of energy selectivity in a wide energy range and polarization sensitivity of the incoming radiation. The first data on Co metal with the new analyser are consistent with previous IRRS spectra and for the first time it was possible to measure the IRRS spectra at the Fe L3,2 of in Co ferrite. Results on Co metal demonstrate the feasibility of linear polarization analysis of the photons emitted from the sample. [1] L. Braicovich, A. Tagliaferri, G. van der Laan, G. Ghiringhelli, N.B. Brookes, Phys. Rev. Lett. 90, 117401(2003) [2] L. Braicovich, G. van der Laan, G. Ghiringhelli, A. Tagliaferri, N.B. Brookes, Phys. Rev. B, 66, 174435 (2002) [3] G. van der Laan, G. Ghiringhelli, A. Tagliaferri, N.B. Brookes, L.Braicovich, Phys. Rev. B,69, 104427 (2004)

41

Elasticity of Hcp-cobalt at high pressure studied by inelastic x-ray scattering

D. Antonangeli1, M. Krisch1, G. Fiquet2, C. Aracne3, J. Badro2, D. Farber3, F.

Occelli3, H. Requardt1

1European Synchrotron Radiation Facility (F). (antonangeli@esrf.fr)

2Insitut de Physique du Globe de Paris, Universite' Paris VI (F). 2Lawrence Livermore National Laboratory (USA).

Characterizing the effect of pressure on the propagation of elastic waves in condensed matter is singularly important for understanding elasticity, mechanical stability of solids, material strength, inter-atomic interactions and phase transition mechanisms. Experiments in such extreme conditions are, however, extremely challenging and most of the currently employed techniques present limitations in either the highest attainable pressure, in the choice of materials, or in the information contents. Inelastic X-ray scattering (IXS) is instead particularly well suited to study samples in extreme conditions. Thanks to the high brilliance of third generation synchrotron sources and efficient focusing schemes, samples with a volume as small as 10-5 mm3 or even less can be probed. This in turn permits the use of diamond anvil cells (DAC), and therefore to explore pressure ranges to and above the Megabar. Sound velocities (and consequently elastic moduli) can be directly derived from the linear part of acoustic phonon dispersion curves with an accuracy of few percent. Here we report the first experimental determination of the complete elastic tensor of hcp-cobalt under hydrostatic compression to 39 GPa. These results are complemented by a study on polycrystalline cobalt up to 96 GPa. The choice of cobalt is due to the possibility to undertake a comprehensive study of single-crystalline and aggregate elastic properties over a wide pressure range [1]. Furthermore ab-initio calculations [2] show an analogue behavior with pressure of the elastic moduli of hcp-cobalt and hcp-iron. The knowledge of the elasticity of cobalt might therefore be used to address the important geophysical issue of elastic anisotropy of iron, the main constituent of the Earth's inner core [3].

[1] C.S. Yoo et al., Phys. Rev. Lett. 84, 4132 (2000). [2] G. Steinle-Neumann et al., Phys. Rev. B 60, 791 (1999). [3] D. Antonangeli et al., Earth Planet. Sci. Lett., in press (2004).

42

Metal to insulator transition and local structure in Sr2FeMo1-xWxO6

F. Bardelli1,2, C. Meneghini1, S. Mobilio1,3, Sugata Ray4 and D. D. Sarma4

1Dipartimento di Fisica, Università di "Roma Tre",

Via della Vasca Navale 84, Roma, Italy. 2INFM-GILDA c/o ESRF Grenoble, France.

3INFN Laboratori Nazionali di Frascati, Italy. 4Solid State and Structural Chemistry Unit, Indian Istitute of Science, Bangalore India.

Sr2FeMoO6 oxides [1] and several related compounds of general formula A2B’B”O 6 (A: alkaline earth, B’, B”: heterovalent transition metals) exhibit half-metallic properties and high spin polarization at the Fermi level. They have recently stimulated a large theoretical interest in the field of heavily correlated electron systems; moreover these materials are of interest in applied research as promising materials for magnetic tunnel junctions and spintronic devices. Nevertheless a full understanding of their special properties is still lacking. The Sr2FeMoO6, for example, is an half metallic ferromagnet (FM) with elevated Curie temperature (Tc > 400 K) and presents large magneto-resistance at room temperature [2]. A kind of double exchange interaction (DE) between Fe ions along the Fe-O-Mo-O-Fe chains mediated by Mo, has been proposed to explain the metallic state and the magnetoresistance. The strangeness of this model is the high Curie temperature, well above that observed in the well known Mn-perovskites (La1-

xCaxMnO3, La1-xSrxMnO3 and related systems), which implies a huge exchange interaction despite the very long distance among Fe ions (~8 Å) [3]. Half metallic properties on Sr2FeMoO6 sensitively depends on Fe-Mo cation order on the B site of the A2B’B”O 6 double perovskite structure. Doping with W substituting for Mo ions in Sr2FeMo1-xWxO6 improves the B-site Fe-Mo/W ordering [4]. The Sr2FeWO6 is an antiferromagnetic (AFM) insulator, thus the doped system Sr2FeMo1-xWxO6 undergoes a metal to insulator (MI) transition and AFM-FM transition as a function of composition. The doped compounds remain (half-) metallic with high Tc >> RT (Room temperature) on a wide range of W concentrations (0<x<0.7). The nature of the transition is still matter of debate and different possible scenarios are proposed: i) a collective valence transition from Fe3+-(W,Mo)5+ in the metallic state to Fe2+-(W,Mo)6+ in the insulating state; ii) a percolation process in which the nominal valence for W and Mo remain 6+ and 5+ respectively at each composition and conductivity is given by metallic Mo-rich clusters embedded in the insulating W-rich regions. Finally a combination of the two effects has been suggested[5]. Detailed knowledge of the microstructure across the metal to insulator transition should help in understanding the origin of magneto-transport properties of these compounds. This study reports the evolution of Sr2FeMo1-xWxO6 local structure as a function of composition as resulting from accurate analysis of Sr, Fe, Mo, and W x-ray absorption spectroscopy. Data were recorded at the Italian beam-line (GILDA-BM8) of the ESRF. The comparative analysis of near edge regions (XANES) of Fe (K-edge), Mo (K-edge) demonstrates that the local structure around the Fe and Mo ions changes steeply across the M-I transition. On the contrary the local structure around W remains almost unchanged as a function of x. The analysis of the extended regions of the spectra (EXAFS) was performed taking into account both single and multiple scattering contributions till about 5 Å from the absorber. Accurate microstructure evolution as a function of composition is reported. The structural results confirm the presence of a

43

step-like structural transition accompanying the MI transition as a function of W doping. 1) A. W. Sleight and J. F. Weiher, J. Phys. Chem. Solids 33, 679 (1972). 2) K. I. Kobayashi and T. Kimura and H. Sawada and K. Terakura and Y. Tokura, 395, 677 (1998). 3) D. D. Sarma, Current Opinion in Sol. Stat. and mat. Science 5, 261 (2001). 4) K.-I. Kobayashi, T, Okuda, Y. Tomioka, T. Kimura, and Y. Tokura J. Magn. Magn. Mat. 218, 17 (2000). 5) S. Ray, A. Kumar, S. Majumdar, E. V. Sampathkumaran and D. D. Sarma, J. Phys. Cond. Mat. 13, 607 (2001).

44

Activity at the BEAR beamline

F.Borgatti, B.Doyle, A.Giglia, N.Mahne, M.Pedio and S.Nannarone

TASC-INFM Laboratory

BEAR (Bending magnet for Emission, Absorption and Reflectivity) beamline is placed at the 8.1 bending magnet port at ELETTRA and is operative since January 2003. The beamline operates in the 3 eV - 1600 eV energy region. The typical spot size is of the order of 10 × 100 µm2 (vertical × horizontal) with an energy resolution ∆E/E ranging from 5000 from 1500 (≈ 4000 at the O K edge). The beam polarization can be changed through a specific device to collect only the upper or lower part of the beam (e.g.: we estimated a circular polarization degree of ≈ 70% at the L2,3 edge of Cobalt). The BEAR end station – based on preparation and scattering chamber - has been conceived to operate in ultra high vacuum featuring a surface science sample environment. Preparation chamber features sample preparation facilities including MBE evaporators, ion sputtering and annealing together with characterizations tools including LEED and AES. Installation of custom chambers can be considered. The scattering chamber features a high degree of flexibility in the experimental geometries. It is intended for optical absorption (also dichroic), light scattering (specular and diffuse reflectivity), photoemission including core level, angle resolved valence band spectroscopy and photoelectron diffraction (further details can also be found at http://new.tasc.infm.it/research/bear/). Examples of typical results will be presented.

45

Local environment of Fe atoms at the Fe/MgO(001) and Fe/NiO(001) interfaces

F. Boscherini1, P. Luches2, S. Benedetti2, M. Liberati 2, I.I. Pronin 3, S. Colonna4, S. Valeri2

1 INFM and Dipartimento di Fisica, Università di Bologna

2 INFM-S3 Modena 3A.F.Ioffe Physico-Technical Institute, St.Petersburg, Russia

4 Istituto di Struttura della Materia – CNR, Roma

Research studies on magnetoelectronic devices based on spin dependent tunnelling and on exchange bias have seen a wide diffusion in recent years, due to the appealing perspective of producing extremely high density magnetic memories. These devices are composed of two ferromagnetic (FM) layers separated by a non magnetic (NM) layer. The coupling of one of the two FM with an antiferromagnetic (AFM) layer is used to pin its magnetization to a certain direction. A detailed characterization of interfaces between FM and AFM or NM materials is essential to understand and quantify the magnetic processes on which the devices are based. Therefore we have performed a structural and chemical characterization of the Fe/MgO(001) and of the Fe/NiO(001) interface, as prototypes of a FM/NM and of a FM/AFM interface, respectively. The characterization has been done by x-ray photoemission spectroscopy (XPS), x-ray photoelectron diffraction (XPD) and x-ray absorption spectroscopy (XAS). Part of the measurements have been performed on-campus, using the S3 laboratories, while the XAS measurements have been performed using synchrotron radiation facilities, namely ELETTRA (BEAR beamline) and ESRF (GILDA beamline). The MgO and NiO substrates are in the form of thin (10 ML) films grown on Ag(001), in order to mimic the real systems and to avoid charging problems. The Fe films have shown a good epitaxy on both MgO(001) and NiO(001), expected on the basis of the small lattice mismatch with the chosen substrates. In the Fe/MgO case, the interface has been found to be rather sharp with no relevant Fe oxidation, as shown by both XPS and Fe L-edge XAS. At the Fe/NiO interface XPS showed a consistent reduction of the NiO layer in contact with Fe atoms, whereas XPD revealed the presence of a bcc Fe-Ni alloy at the interface involving up to 3 ML. Angle-dependent XAS at the Fe K-edge has then been used to determine the local atomic environment of Fe atoms and in particular the presence and the distribution of O atoms within the Fe layer at the interface. The importance of the interface processes on the spin couplings at the two interfaces is discussed.

46

X-ray Absorption study of the local structure of boron atoms in silver borate glasses

R. Carboni1,C. Armellini 2, M. Malvestuto1, F.Rocca2, F. Boscherini1.

1 INFM and Dept. of Physics, University of Bologna (I).

2IFN-CNR, Inst.for Photonics and Nanotechnologies, Sect. "ITC-CeFSA" of Trento (I). Silver-oxide borate glasses (Ag2O – nB2O3) are interesting due to their application in the realization of fast ion conducting (FIC) glasses, especially when mixed with AgI, which enhances by several orders of magnitude the ionic conductivity. In general, the addition of a metal oxide (as Ag2O) to B2O3 induces a transition from a trigonal to a tetrahedral coordination of boron atoms, due to the transfer of an electron from a silver oxide unit to boron. The quantification of the relative number of differently coordinated boron atoms is very useful in order to understand the structural modifications consequent to silver oxide alloying, and to build a comprehensive structural model. This is normally done by NMR spectroscopy, but some recent works have shown that X-ray absorption spectroscopy (XAS) may provide important information, mainly to detect tetrahedral units in the low concentration range and to investigate possible near surface structural modifications. We have performed a fluorescence-detected Boron K-edge XAS experiment on the BEAR beamline of the ELETTRA facility. High energy resolution near edge spectra as a a function of Ag2O content in AgI-free binary glasses [Ag2O – n(B2O3)] for n = 2, 3, 4, 6, 8 and as a function of AgI in ternary glasses (xAgI)+ (1-x) [Ag2O – n(B2O3)], (with x = 0 to 0.55 and Ag2O relative concentration fixed to n = 2) have been measured. Accurate measurements with x-ray fluorescence detection have been performed at different angles of incidence to quantify and correct the self-absorption effect. A clear evidence of near surface structural modifications is shown in vitreous B2O3 samples. Significant changes of the spectral features related to the Boron coordination are present for different concentration of Ag2O and AgI. Data analysis is in progress to quantify the relative concentration of three- and four-fold coordinated Boron atoms and to evaluate the sensitivity of XAS to the modifications of non-bridging oxygen bonds produced by varying the content of Ag ions. A comparison with the available information on the superstructural units (diborate, tetraborate, pentaborate,…) where many different BO3 and BO4 groups are differently linked together to form the borate glass network is performed.

47

Characterization of Mg- and Al-site geometries of wiluite and vesuvianite using XANES.

G. Cibin, A. Mottana, G. Della Ventura and F. Bellatreccia.

Dipartimento di Scienze Geologiche, Università di Roma Tre (I).

(cibin@lnf.infn.it)

Wiluite, Ca19(Al,Mg,Fe,Ti)13(B,Al,□)5Si18O68(O,OH)10, is the B-rich equivalent of vesuvianite recently characterized from a sample of Wilui River, Sakha Republic, Russian Federation, and found within a serpentinite associated with grossular and serpentine minerals. Vesuvianites are known to host their non-tetrahedral cations in four types of coordination sites, which are, respectively, eight- (X), five- (Y1), and six-fold (Y2 and Y3) coordinated. While the six-fold preference of the small Al, Ti and Fe3+ cations for the two irregular and distorted Y2 and Y3 sites is well-established, much is still argued about the ability of the divalent cations Mg, Mn, and Fe2+ to enter the different sites. In wiluite Mg is expected to be partitioned over three distorted sites, and over the Y1 site, by itself unusual for being in the rare square-pyramidal configuration in vesuvianites; in our wiluite, the X-ray structural refinement (Xref) shows that the Y1 polyhedron undergoes a further distortion, from squat to elongated. In order to verify divalent cation distribution in wiluite, we recorded Mg K-edge XANES spectra. The collected spectrum suggests that Mg is distributed over a variety of sites that differ in shape but not so much in local energy. By contrast, the reference vesuvianite spectrum shows neatly separated features, generated by five-fold coordinated Mg, and by the six-fold coordinated one. To cross-check the results on divalent Mg, we determined the coordination environment for Al, a cation that cannot be anything else but trivalent and that XRef state to be only in the Y3 and Y2 octahedra. The Al-XANES spectra of wiluite and vesuvianite are typical for Al in octahedral coordination and are nearly identical in their energies, thus suggesting that Al is located in the same environments in both minerals.

48

Near Edge X-ray Absorption Fine Structure Spectroscopies On Methyl-Oxiranes Vapour: Experiment And Theory

G. Contini, S. Turchini, N. Zema, T. Prosperi

Istituto Struttura della Materia, C.N.R., Via Del Fosso del Cavaliere 100, 00133 Roma, Italy Near edge X-ray absorption fine structure (NEXAFS) spectra of methyl-oxirane (C3H5O) have been investigated from experimental and theoretical point of view. The electronic structure of methyl-oxirane is of great interest since this compound is a chiral building block for several asymmetric synthesis and is a good test molecule because its conformational rigidity makes it amenable to extensive calculations and to mono-signated absorption bands and dichroic effects. NEXAFS experimental spectra of methyl-oxirane in vapour phase have been recorded at the Carbon and Oxygen K-edges to probe the electronic structure of both unoccupied orbitals; the experimental data are discussed by comparison with static-exchange (STEX) ab initio calculation for the two edges. A general good agreement is observed between experimental and theory, allowing a detailed discussion and attribution of the various observed features. Vibrational effects on the C K-edge is also identified in the high resolved experimental spectra. The experimental NEXAFS spectra were taken at Elettra (Trieste, Italy) on the Circular Polarisation beam line equipped with a Samson-like double ionisation absorption cell working in total ion yield mode, to provide a quantitative measurements of the absorption structures.

49

XRD study of Tb3+-doped silica gel

N. Diab1, G. Dalba1, F. Rocca2 and C. Meneghini3

1 INFM and Dipartimento di Fisica, Università di Trento, Via Sommarive, 14 - I-38050 Povo (Trento), Italy.

2 IFN, Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche - Sezione “ ITC-CeFSA” di Trento, via Sommarive 18, I-38050 Povo (Trento), Italy

3 INFM - GILDA Crg at ESRF, Grenoble, France and Dipartimento di Fisica "E. Amaldi", Università di Roma Tre, Roma, Italy .

Silica based sol-gel glasses activated by rare-earth (RE) ions are attractive materials for integrated optics devices. The optical properties of these materials can be tuned by changing the densification process and by varying the type and the concentration of the RE ions or by co-doping with other ions. Our purpose in this work is to explore the local environment around the RE ion inside the host glass and to see the possibility of the formation of RE-RE bonds at short-range distances. The later being an undesired process for the function of those materials. We present X-ray scattering measurements on Tb3+ doped silica xerogels as a function of Tb content and thermal treatment. Silica gel samples were prepared following the standard procedure of sol gel route. Tb concentration was varied from 400 and up to 40000 ppm Tb/Si. Two categories of samples are presented: as prepared samples (labelled NT) and samples densified at 900oC (labelled T). XRD spectra were collected using X-ray powder diffractometer in transmission geometry, with a flat image plate as a detector. Diffraction data were analysed using the Gildaxs software package. Radial distribution functions (RDFs) were calculated for all samples. Due to the very short reciprocal space range, Tb peaks were not resolved from the contributions of the host network. To overcome this problem, the differential radial distribution functions (dRDFs) were calculated, by subtracting the contribution of the undoped silica gel spectra. The results show that in the case of NT samples Terbium is bonded to Oxygen atoms at distance ~2.30 Å. After densification, a Tb-Si correlation is present, at a distance ~3.6 Å. Furthermore, for the largest Tb contents (~40000 ppm Tb/Si) a long-distance correlation is also detectable as a broad peak centred at ~7 Å. We assigned such broad structure to Tb-Tb interaction. However, our results do not show any evidence of Tb-Tb short-range distance within the studied concentrations.

50

X-ray Absorption and Photoelectron Spectroscopy studies of graphite and single-walled carbon nanotubes: the oxygen

effect

I. Davoli1,Z.Y. Wu2, M. Abbas2, K. Ibrahim 2, J.Zhong2, M.L. Terranova3, S. Orlanducci3, V. Sessa3, A. Fiori3,

1 Dipartimento di Fisica, Università di Roma “Tor Vergata”, 00133 Roma, Italy

2 Beijing Synchrotron Radiation Facility, I.H.E.P., P.O. Box 918, 100039 Beijing, China 3 Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma “Tor Vergata”, Roma 00133. Italy.

X-ray Absorption and Photoelectron spectroscopies have been performed on well characterized highly oriented pyrolitic graphite (HOPG) and single walled carbon nanotube samples before and after annealing treatments in ultra high vacuum. At the C K edge we observed that an absorption feature detected between the π* and σ* structures, previously assigned to free electron like interlayer states, disappear after in situ annealing treatment. In the photoelectron spectra a similar behavior is observed addressing the origin of these features to surface contamination. The same spectra have been collected after aging in air on the same samples showing the reappearance of the original feature which we assign to surface oxygen adsorption.

51

Magnetic properties of Sr2FeMoO6 thin films: grown by pulsed laser deposition

A. Di Trolio, R. Larciprete, G.Parisi

CNR-IMIP, Sez. Potenza, Zona Industraile 85050 Tito Scalo (PZ), Italy

N. Zema, S. Turchini, D. Fiorani, A.Testa CNR-ISM, Via del fosso del cavaliere 100, 00133 Roma, Italy

Ordered double perovskite Sr2FeMoO6 (SFMO) exhibits in its polycrystalline bulk form a Curie temperature (Tc) of about 415 K and a pronounced negative magnetoresistance, which make it a potential candidate for applications in spin valves and magnetic tunnel junction devices. Epitaxial SFMO thin films can be grown on SrTiO3 single crystal substrates by Pulsed Laser Deposition (PLD) using a Nd-Yag laser operating at 532 nm. In this study our aim was to determine the influence of laser fluence on the structural and functional properties of SFMO layers deposited by PLD. For samples deposited at fluence of about 2 J/cm2 the magnetisation loops showed a sharp ferromagnetic transition and a low coercitivity, as well as a ferromagnetic transition temperature of about 330 K and a saturated magnetisation of 2.8 µB/f.u. These values are indicative of a prevalent ferromagnetic phase generating a long range order of the magnetic domains. The good magnetic properties of the samples were confirmed by X-ray magnetic circular dichroism (XMDC) experiments performed with elliptically polarised synchrotron radiation at the Circular Polarisation beamline of ELETTRA (Trieste, Italy). The polarisation-dependent X-ray absorption spectra measured at the Fe 2p edge with helicity parallel and antiparallel to the Fe 3d majority spin indicated the presence of. substantial magnetic moment at the Fe site, reproducing the result obtained in the case of bulk polycrystalline samples. Preliminary XMDC results at the Mo3p edge not reported here, showed the lack of a measurable dichroism at the Mo site. These results led to the conclusions that, in analogy with polycrystalline samples, the valence of Fe atoms is 3. Disordered lattice structure, leading to poor magnetic response are obtained at laser fluence of the order of 6 J/cm 2. In this case the structural and magnetic analysis demonstrated that the resulting ablation conditions are deleterious for the achievement of well ordered double perovskite layers because the excess of kinetic energy of the species impacting the growing film promote lattice disorder, especially related to a high concentration of Fe/Mo anti-site defects.

52

Angle resolved resonant inelastic x-ray scattering from transition-metal magnetic ions

P. Ferriani and C. M. Bertoni

INFM, National Research Center on nanoStructures and bioSystems at Surfaces S3

and Dipartimento di Fisica, Università di Modena e ReggioEmilia, Via Campi 213/A, 41100 Modena, Italy

Thanks to the progress of synchrotron radiation sources resonant inelastic x-ray scattering (RIXS) has become a powerful technique of increasing interest for the study of electronic and magnetic properties of solids [1]. The higher selectivity with respect to x-ray absorption spectroscopy (XAS), due to the choice of the de-excitation channel and the propagation direction of the outcoming photons, allows to obtain information not accessible in XAS. The study of the angular distribution of the emitted photons allows to recover: (i) information on the core-hole created in the absorption step [2]; (ii) the multipole moments of the charge and magnetic densities of the partially filled shells in the atomic ground state, through the use of sum rules that have been developed theoretically[3]. In the perpendicular geometry, where the incident beam impinges orthogonally with respect to the magnetization, XAS shows no magnetic dichroism, while a dichroic signal can be detected in angle resolved RIXS. Its origin is linked to the creation of a polarized core hole in the absorption step and it is detectable only in presence of a nonvanishing projection of the emission direction along the magnetization. Thus the study of the angle and polarization dependence of the RIXS cross-section is of great importance. A convenient formalism was developed by Fukui [4] for the case when the magnetization belongs to the scattering plane. A recent demonstration by L. Braicovich et al. [5] of the quantitative recovery of the multipole moments up to order four, when the magnetization and the incident and emitted beam do not belong to the same plane, suggests the extension to the general case. In this work the expression for the angle dependent cross-section in the dipole-dipole channel is given in the most general geometrical setup, both for the total value summed on the two incoming beam polarization and for the circular dichroism, as explicit functions of the angles defining the directions of the ingoing and outgoing beams, so that it can be used for the comparison with experiments. We consider the transitions 2p63dn

→2p53dn+1→2p63s13dn+1. The case where the propagation of the emitted photon

is out of the plane defined by the direction of the incident photon and the sample magnetization is investigated in detail, highlighting the importance of the interference among the intermediate states. In this case an asymmetry for emission with respect to that plane is found. Its origin is linked to the presence of the magnetization. Particular relevance is given to the perpendicular geometry, where numerical calculations performed for the L3 threshold of some 3d transition metals systems are supplied. The pedagogical case of the Ni2+ in cylindrical symmetry is discussed following step by step the calculations. The effects of the temperature and of the crystal field are also discussed.

References

[1] A. Kotani and S.Shin, Rev. Mod. Physics, 73, 203 (2001) [2] G. Van der Laan, J. Electron Spectrosc. Relat. Phenom. 101-103, 859 (1999)

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[3] P. Carra, M. Fabrizio and B.T. Thole, Phys. Rev. Lett. 74, 3700 (1995) [4] K. Fukui, H. Ogasawara, A. Kotani, T. Iwazumi, H. Shoji and T. Nakamura, J. Phys. Soc. Japan70, 1230 (2001) and 70, 3457 (2001) [5] L. Braicovich, A. Tagliaferri, G. van der Laan, G. Ghiringhelli and N.B. Brookes, Phys. Rev. Lett. 90, 117401 (2003)

54

The structural role of Ag in galena (PbS): a xanes study

G. Giuli 1, E. Paris1, Z. Wu2, S. De Panfilis3, G. Pratesi4, C. Cipriani4

1 Dip. di Scienze della Terra e Unita’ INFM - Universita’ di Camerino, Italy;

2 Beijing Synchrotron Radiation Center – Beijing, P.R.China; 3 ESRF – Grenoble, France;

4 Dip. di Scienze della Terra - Universita’ di Firenze, Italy. In spite of its precious metal nature, Ag can be in sulfides as a trace impurity in solid solution. Ag-bearing galena (PbS) is to date the biggest source for Ag extraction in the world. In galena Ag partly substitutes for Pb, and partly form micro-inclusions of diaphorite. However, to date there is no unique assignment of Ag location into the PbS structure. Substitution can be attained by two exchange reactions. The first, 2Ag+=Pb2+, can lead only to modest Ag enrichment because half of the Ag should be located in interstitial sites. The second exchange reaction, Ag++(Sb,Bi)3+= 2Pb2+, can lead to higher Ag contents. To understand whether Ag is located in an interstitial site or in the Pb site (or in both), and to obtain Ag coordination number and Ag-S distance we performed a XAS analysis at the Ag K-edge. The data have been collected at ESRF (Grenoble) on Ag-bearing galena samples and standards, also characterised by micro-chemical, XRD and TEM analyses. The analysis of Ag amounts as low as 500 ppm in a Pb-rich matrix is a complex experimental problem which has been overcome by recording the spectra in fluorescence mode using a Ga-filter to reduce the Pb fluorescence. The galena XANES spectra have been compared with theoretical spectra simulating the presence of Ag in the tetrahedral interstitial site (–43m) or in the octahedral Pb site (m3m). The comparison shows that Ag can occur in both sites and that the experimental spectra can be fitted combining the spectra in the proportion 50% and 50%. Also some galena spectra compare well to that of diaphorite, suggesting that when inclusions are present, most Ag partitions into the inclusion and only in minor proportions into the galena solid solution.

55

O K-edge X-ray absorption study of ultrathin NiO epilayers deposited in-situ on Ag(001)

E. Groppo1, C. Prestipino1, C. Lamberti1, R. Carboni2, F. Boscherini2, P. Luches3,

S.Valeri3, S. D’Addato3

1Department of Inorganic, Physical and Materials Chemistry, and NIS centre of excellence,

University of Torino and INFM - U.d.R. di Torino (I). 2INFM and Dipartimento di Fisica, Università di Bologna (I).

3 INFM- National Center on nanoStructures and bioSystems at Surfaces (S3) and Dipartimento di Fisica, Università di Modena e Reggio Emilia, Modena (I).

In this contribution we used polarization-dependent, O K-edge, X-ray absorption spectroscopy (XAS) to probe the structure of ultra-thin NiO epilayers deposited on Ag(001), in the 3-50 ML thickness range. The work is complementary to our recent Ni K-edge XAS studies on the same system [1,2]. Differently from this case, where the samples were measured ex-situ and a 5 ML-thick MgO cap was used to avoid the hydroxylation of the NiO film, the NiO epilayers were grown in-situ in the end station of the ALOISA beamline of the ELETTRA facility. A quantitative analysis of the data in the extended energy range has been performed using multiple scattering simulations. We found that, even in the ultrathin limit, the local structure of the film is rock-salt and we obtained a quantitative evaluation of the average in-plane and out-of-plane film strain as a function of the film thickness T. An in-plane compressive strain, due to lattice mismatch with the Ag substrate, is clearly present for the 3 ML film, being the in- and out-of-plane nearest neighbor distances equal to //r = 2.048 ± 0.016 Å and ⊥r = 2.116 ± 0.018 Å. These values are in agreement

with the expected behavior for a tetragonal distortion of the unit cell. The growth-induced strain is gradually released with increasing T: it is still appreciable for 10 ML but is completely relaxed at 50 ML. Any significant intermixing with the Ag substrate has been ruled out. The XAS technique becomes self consistent in the determination of the NiO/Ag(001) interface when the Ni K-edge data are coupled with the O K-edge ones. Combining O and Ni K-edge results, we concluded that NiO films grow on Ag(001) in the O-on-Ag configuration, with an interface distance d = 2.28 ± 0.08 Å. This expansion of the interplanar distance is in agreement with recent ab-initio simulations and seems to be a general feature, since a significant expansion has been observed also for the similar MgO/Ag(001) system [3].

[1] C. Lamberti, E. Groppo, C. Prestipino, S. Casassa, A. M. Ferrari, C. Pisani, C. Giovanardi, P. Luches, S. Valeri, and F. Boscherini, Phys. Rev. Lett. 91, 046101 (2003). [2] P. Luches, E. Groppo, C. Prestipino, C. Lamberti, C. Giovanardi, and F. Boscherini, Nucl. Instr. Meth. B 200, 371 (2003); E. Groppo, C. Prestipino, C. Lamberti, P. Luches, C. Giovanardi, and F. Boscherini, J. Phys. Chem. B 107, 4597 (2003). [3] P. Luches, S. D'Addato, S. Valeri, E. Groppo, C. Prestipino, C. Lamberti, and F. Boscherini, Phys. Rev. B 69, 045412 (2004); P. Luches, E. Groppo, S. D'Addato, C. Lamberti, C. Prestipino, S. Valeri, and F. Boscherini, Surf. Sci., in press (2004).

56

Local structure and magnetotransport in Sr2FeMoO6 double perovskite compounds: an EXAFS study

F. Liscio1, F. Bardelli1,2, C. Meneghini1, S. Mobilio1,3, Sugata Ray4 and D. D.

Sarma4

1Dipartimento di Fisica, Università di "Roma Tre",

Via della Vasca Navale 84, Roma, Italy. 2INFM-GILDA c/o ESRF Grenoble, France.

3INFN Laboratori Nazionali di Frascati, Italy. 4Solid State and Structural Chemistry Unit, Indian Istitute of Science, Bangalore India.

Sr2FeMoO6 oxides with double perovskite structure1 are half metallic ferromagnetic with elevated Curie temperature (Tc > 400 K) and present large magnetoresistance at room temperature2. In the last few years these compounds stimulated large interest as potential electrodes in magnetic tunnel junction and innovative spintronic materials. On the other hand these peculiar magnetic and electronic properties attracted the fundamental research in the field of heavily correlated electron systems. Their crystallographic structure derives from the ideal cubic perovskites: it is made of weakly tetragonal distorted cubic units with the Sr ions located at the center and the Fe(Mo)O6 sharing the cube edges. The regular alternation of Fe and Mo along the lattice edges (chemical order) strengthens the magnetoresistance, on the other hand the increase of miss-site defects (chemical disorder) weakens the magnetoresistance. A kind of double exchange interaction (DE) between Fe ions along the Fe-O-Mo-O-Fe chains mediated by Mo, has been suggested to explain the metallic state. Chemical disorder reduces the DE coupling and gives rise to tunnel type conductibility. The most striking features in this picture is the high Curie temperature, well above that observed in the well known Mn-perovskites (La1-xCaxMnO3, La1-xSrxMnO3 and related systems), which imply huge exchange interactions despite the very long distance among Fe ions (~8 Å)3. This work proposes a detailed EXAFS study on two Sr2FeMoO6, a fully chemically ordered and a fully chemically disordered sample, in order to get insights on the micro-structural origin of their magnetotransport properties. X-ray absorption experiments were performed at the Italian beamline (GILDA-BM8) at the ESRF. In order to have a complete and exhaustive description of local order Fe K-edge (~7112 eV), Mo-K edge (~20000 eV) and W-LIII (~10200 eV) edge EXAFS data were analysed. The complete EXAFS spectra were refined taking into account for single as well multiple scattering contributions till about 6 Å. This permitted to probe the relative arrangement of Fe and Mo ions. The coherence of the structural models, as resulting from the three edges analysis strengthens and gives confidence on the results. The main result is that either ordered and disordered compounds show very similar chemically ordered local structure, i.e. the presence of Fe-Fe and Mo-Mo coordination is weak (almost negligible) in both the samples. These finding contrasts with the information from X-ray diffraction analysis, i.e. a high ordered (order parameter ~ 90%) and a completely disordered sample. Our results suggest that the long-range chemically disordered sample is made of small (20-30 Å) chemically ordered clusters. Such a small size would produce weak and broad superlattice reflections easily confused with the background in standard diffraction patterns. 1) A. W. Sleight and J. F. Weiher, J. Phys. Chem. Solids 33, 679 (1972). 2) K. I. Kobayashi and T. Kimura and H. Sawada and K. Terakura and Y. Tokura, 395, 677 (1998). 3) D. D. Sarma, Current Opinion in Sol. Stat. and mat. Science 5, 261 (2001).

57

High dielectric constant Y2O3 ultra thin films on Si (001): a structural study

M. Malvestuto1, F. D’Acapito2, F. Boscherini1, S. Spiga3, M. Fanciulli3,

A. Dimoulas4, G.Vellianitis4, G. Mavrou4

1INFM and Physics Dept., University of Bologna, Italy; 2INFM-OGG c/o ESRF, GILDA CRG, Grenoble, France; 3Laboratorio MDM-INFM, I-20041 Agrate Brianza. Italy; 4MBE Laboratory, Institute of Material

Science, National Center for Scientific Research Demokritos, Athens, Greece.

The scaling down of the gate dielectric thickness in CMOS devices is prompting the search for alternative high dielectric constant (high-κ) materials to replace thermally grown silicon dioxide. Key requirements of a successful high-κ candidate are a good structural and electrical properties and high quality interfaces between the high-κ film and the Si substrate. Y2O3 is a good candidate for SiO2 replacement due to its predicted thermodynamic stability in contact with Si and its relatively high κ value (14-18). We report a structural study of Y2O3 ultra thin films and of the Y2O3/Si interface by combined Y and O K-edge x-ray absorption spectroscopy (XAS). XAS measurements at the Y K-edge were performed at the GILDA beam line (ESRF), using a grazing incidence geometry to enhance surface sensitivity. O K-edge measurements were performed at the BEAR beamline of ELETTRA (Italy). Examples of the data are reported in the figures. Y2O3 films, 2 to 20 nm thick, were grown on Si(001) by electron beam evaporation in an MBE system; some samples were subsequently annealed in-situ. Analysis of the XAS data, both in the near-edge and extended energy ranges, was performed with the aid of ab-initio simulations in the framework of multiple scattering theory. The parallel analysis of the O and Y XAS has allowed to obtain a rather complete picture of the local structure as a function of thickness and annealing. While the thickest films (20 nm) have a local atomic and electronic structure very similar to that of bulk yttria, significant

Fig. 1: FT of Y edge EXAFS as a function of thickness and annealing conditions.

Fig. 2: XANES at the O edge for the films; φ is the angle between the surface and the x-ray electric field.

58

structural disordering occurs with decreasing thickness; annealing reduces these structural distortions. We demonstrate the presence of a quite complex interface structure, which includes the formation of silicon oxide and, in the as-deposited films, the presence of Y-Si bonds, suggesting a partial interface instability of Y2O3/Si(001).

59

Macroscopic investigation of ferroelectric and antiferroelectric structures using X-ray resonant scattering

Ivan Marri 1

1 INFM, National Research Center on nanoStructures and bioSystems at Surfaces S3 and Dipartimento di Fisica, Università di Modena e ReggioEmilia,

Via Campi 213/A, 41100 Modena, Italy (marri@unimo.it)

Near-edge x-ray scattering spectroscopy is a power technique in the study of microscopic properties of matter; it allow a direct determination of the electric and magnetic properties of the valence electron state expecially in transition metal, rare earths and actinides. Using a single ion model and considering only resonant processes controlled by electric dipole (E1) and electric quadrupole (E2) transitions, a number of authors pointed out the possibility to express the scattering amplitude in terms of simple spin-orbital moment operators of the valence shell involved in the resonance. Recently, a number of pubblications have stressed the importance of E1-E2 transitions for interpreting unexpected peaks in certain x-ray resonant diffraction spectra; Templeton and Templeton [1] have pointed out the importance of E1-E2 terms in the tetrahedral anisotropy of x-ray anomalous diffraction in noncentrosymmetric crystals for weak or forbidden Bragg reflection; Elfimov et al. [2] have used E1-E2 interference to analyse the (600) and (222) resonant x-ray Bragg reflection near the germanium K-edge. To fully exploit the informations contained in the E1-E2 resonant processes we will study the fE1-E2 scattering amplitude. Using Wigner-Eckart algebra, neglecting the energy dispersion of the intermediate states, fE1-E2 will be express in terms of effective one electron operators and its polar and magnetoelectric contributions, with their orbital nature, will be identified.

References [1] D.H. Templeton and L.H. Templeton, Phys. Rev. B, 49, 14850 (1994). [2] I.S. Elfimov et al. Phys. Rev. Lett. 88, 015504 (2002)

60

Crystal Structure of the regulatory protein StyR from Pseudomonas fluorescens

M. Milani 1, L. Leoni2, M. Bolognesi3.

1Istituto Giannina Gaslini, Genova (I).

2Dipartimento di Biologia, Universita' “Roma3” (I). 3Dipartimento di Fisica, Universita' di Genova (I).

(bolognes@fisica.unige.it)

StyS and StyR constitute a two-component regulatory system that controls styrene catabolism in Pseudomonas fluorescens. The catabolic pathway is activated when StyR is phosphorylated by the sensor kinase StyS. StyR is constituted by two domains: a N-terminal receiver domain (STyR-N) and a C-terminal transcriptional-activator domain (StyR-C). The phosphorylation of STyR-N produces its dimerization, activating StyR-C-DNA binding. As a first step in unravelling the structural bases of signal transfer between the two domains, leading to protein activation, we have solved the StyR 3D structure in the monomeric/inactive state. The diffraction data were collected at ESRF beam line ID14-3 at λ = 0.931 Å , reaching 2.2 Å resolution. The crystal structure was solved by molecular replacement using two independent models for the two domains. Refinement is still in progress. StyR crystals belong to the monoclinic P21 space group, and accommodate one monomer in the asymmetric unit. Nevertheless, tight association between StyR chains is observed in the crystals. Notably, one hexacooridnated Mg2+ ion is observed as well structured in the StyR-N domain, at the Rossmann fold topological switch point, where phosphorylation is expected to occur. The two constituent domains are separated by an elongated α-helix.

61

EXAFS study of cadmium under high pressure and high temperature conditions

M. Minicucci 1, P. Rocci1, A. Di Cicco1, A. Trapananti1,

S. De Panfilis2,G. Aquilanti 2

1INFM and Dipartimento di Fisica, Universita' di Camerino, I-62032 Camerino (MC) Italy

2European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble, France.

Liquid and solid cadmium has been investigated in a wide pressure and temperature range in order to provide new information about structure and transitions occurring in this metal. X-ray absorption, single-energy temperature scans and energy scanning x-ray diffraction data were collected in a 300-875 K temperature and 0-5.8 GPa pressure range, exploiting the setup available at the ESRF-BM29 beam-line. Clear changes in the absorption spectra (measured at cadmium K-edge) and in the diffraction patterns, associated with the solid-liquid transition allowed us to obtain an accurate measurement of the melting curve as a function of pressure. The structural data are compared with the few available calculations and x-ray scattering data on molten Cd at ambient pressure. High pressure data on liquid cadmium are reported for the first time and are essential to shed some light on the changes of the local structure induced by pressure. From EXAFS data analysis Mean Square Relative Displacement of first and second shell respectively, are also determined with accuracy for the solid Cd as a function of pressure giving important information about its vibrational properties.

62

Mn-K edge XANES structural refinement in manganese perovskites

C. Monesi1, F.Bardelli1,2, C. Meneghini1,2, S. Mobilio1,2, M. Benfatto3,

U. Manju4, D. D. Sarma4

1Dip. di Fisica Università Roma Tre, via Vasca Navale 84, 00146 Roma, Italy (monesi@fis.uniroma3.it)

2INFM-GILDA c/o ESRF Grenoble, France 3Laboratori Nazionali di Frascati INFN, Via E. Fermi 40, I-00044 Frascati, Italy

4Solid State and Structural Chemistry Unit, Indian Institute of Science Bangalore, 560012, India

Manganese oxides with perovskite structure play a special role in the field of strongly correlated systems since their peculiar magnetic transport properties. These are due to ferromagnetic double-exchange (DE) and antiferromagnetic super-exchange (SE) interaction among Mn ions, and strong electron-phonon interaction (small and/or large polarons). The balance among these interactions is mainly determined by local atomic structure surrounding Mn ions, characterized by Jahn-Teller (JT) distortions of MnO6 octahedra. Therefore the sensitivity to the short-range order of x-ray absorption spectroscopy (XAS) makes this technique suited to study these compounds as demonstrated by the wide recent literature. In particular the analysis of the XANES region could provide topological information useful to deeply understand the physics of manganites. This work reports the first attempt to a quantitative analysis of Mn K edge XANES on CaMnO3 and LaMnO3 perovskite samples. The local structures obtained by fitting the XANES data are compared with structural models derived by standard EXAFS analysis and diffraction (x-ray and neutron) data analysis. In CaMnO3 the average structure derived from XANES results in good agreement with EXAFS analysis and with the structure found by diffraction. This strengthens the confidence on the MXAN method. In LaMnO3 XAS results reproduce the main structural features as given by XRD, but both EXAFS and XANES suggest reduced Mn-O apical distance, resulting in a Jahn-Teller distortion 15-20 % reduced compared with the coherent distortion obtained by neutron diffraction.

63

Carbon and nitrogen K-edge NEXAFS investigation of novel peptide-based biomaterials for tissue engineering

G.Polzonetti1, C.Battocchio2, M.Dettin3, G.Iucci1, V.Carravetta4, F.Borgatti5, M.Pedio5, N.Mahne

5, A.Giglia5, B.Doyle5, S.Nannarone5

1Department of Physics and unità INFM, INSTM and CISDiC, University “Roma Tre”, Via della Vasca Navale, 84 – 00146 Rome (Italy)

2Department of Chemistry, University "La Sapienza" P.le A.Moro, 5 - 00185, Rome (Italy) (chiara.battocchio@uniroma1.it)

3Department of Chemical Process Engineering, University of Padova, via Marzolo, 9 - 35131 Padova 4IPCF-CNR, Via Moruzzi 1, 56124 Pisa (Italy)

5TASC-INFM, in Area Science Park, SS 14 Km163,5, Basovizza –Trieste (Italy) The development of synthetic materials promoting cell growth aims at the realization of systems suitable for implantology or sensoristic applications. The final goal is to establish methodologies of surface modification based on the controlled adsorption/anchoring of special oligopeptide sequences, synthesized on purpose, capable to give self-organised layers on suitable surfaces. Biomaterial scaffold are components of cell-laden artificial tissues and transplantable sensors. Some of the most promising new synthetic biomaterial scaffolds are composed of self-assembling peptides that can be modified to contain biologically active motifs. Peptide-based biomaterials can be fabricated to give rise to two- and three-dimensional structures. In this contribution we present preliminary results as obtained by near-edge X-ray absorption spectroscopy (NEXAFS), concerning the electronic structure of a 16 units peptide as deposited onto Au and TiO2 substrates. The peptide has been synthesized on purpose to give rise to a special sequence of the constituting amino acids: L-Alanine, L-Aspartic acid and L-Lysine, the difficult task of sample purification has been carried out subsequent to the synthesis. The titanium dioxide substrate has been prepared by growing Ti onto a Si(111) disk and a successive oxidation; XPS data gave confirmation of the surface stoichiometry. Data concerning some basic amino acids used in the sequence are also presented. Measurements have been carried out at both C-K and N-K edges as a function of the incidence angle of the impinging photons with respect to the sample surface. Feature assignment is discussed and preliminary considerations concerning the angular dependence of specific resonances is also reported. Despite the extended and sophisticated structure of the peptides our experimental data will be supported by static exchange ab initio STEX calculations that will give simulations of the expected NEXAFS spectra and of their polarization dependence, allowing a direct comparison between experimental and theoretical data.

64

Dynamics of the fluorescence decay of the doubly excited states of He

K.C. Prince1,2, M. Coreno3,2, R. Richter1, M. de Simone2, K. Bucar4, and M. Zitnik 4

1 Sincrotrone Trieste, I-34012 Basovizza (Trieste), Italy, 2 INFM- TASC, Gasphase beamlie @ Elettra, I-34012 Basovizza (Trieste), Italy,

3 CNR-IMIP, Montelibretti (Rome), I-00016 Italy, 4J. Stefan Institute, 1000 Ljubljana, Slovenia

The doubly excited states of He constitute a prototypical system for testing our understanding of the three-body quantum problem. Recently the importance of fluorescence in the decay of these states [1-3], its influence on cross-section [4] and the excitation of dipole forbidden triplet states [5] have attracted considerable attention. We studied the decay processes occurring after double excitation of the He atom below the N=2 edge by Photon Induced Fluorescence Spectroscopy (PIFS), (a technique demonstrated by Schartner et al [6]), for the n=3-8 singlet states (n+, n-, 2pnd). The first step in the fluorescence channel is emission of a VUV photon leaving the atom in one of several 1sns or 1snd states. Cascade decay to 1sn’p (n’<n) states occurs and by detection of this emission the branching ratios of the first step can be calculated. These branching ratios are compared with theoretical calculations and reasonably good agreement is obtained. In addition PIFS spectra of the decay of the doubly excited 73D and 83D triplet states [5] have been detected, confirming their assignment. This is only the second observation of these states. The technique has been further utilised to observe the Stark effect on the doubly excited states. Recent work [7] has shown strong effects on the absorption spectrum in fields up to 84 kV/cm: we observe significant effects in PIFS at fields an order of magnitude lower, where there are no detectible changes in the absorption spectrum. In particular, the branching ratios for the fluorescent decay change. We interpret this in terms of the electric field causing a mixing of states of even parity which is opposite to the odd parity states excited in field free conditions. References [1] J.-E. Rubensson et al, Phys. Rev. Lett. 83 (1999) 947. [2] T. Ward Gorczyca et al, Phys. Rev. Lett. 85 (2000) 1202. [3] M. K. Odling-Smee et al, Phys. Rev. Lett. 84 (2000) 2598. [4] K.C. Prince et al, Phys. Rev. A. 68 (2003) 044701. [5] F. Penent et al, Phys. Rev. Lett. 86 (2001) 2758. [6] K.-H. Schartner et al, Phys. Rev. A 64, (2001) 040501. [7] J. R. Harries et al, Phys. Rev. Lett. 90, 133002 (2003).

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Resonant photoemission of methanol, formic acid, dimethyl ether and formaldehyde at the oxygen K edge

K. C. Prince1,2, R. Richter1, M. de Simone2, M. Coreno3, H. Farrokhpour 4,5,

and M. Tabrizchi4,5

1Sincrotrone Trieste, Area Science Park, I-34012 Basovizza, Trieste, Italy 2Laboratorio TASC-INFM, Area Science Park, I-34012 Basovizza, Trieste, Italy

3CNR-IMIP, Montelibretti, I-00016Roma, Italy 4The Abdus Salam International Centre for Theoretical Physics, I-34014 Trieste, Italy

5Chemistry Department, Isfahan University of Technology, Isfahan 84154, Iran Resonant photoemission spectra at the oxygen 1s edge of a series of small oxygen-containing organic molecules have been measured. The resonant decay spectra of methanol and formic acid show two classes of features: resonantly enhanced valence bands that disperse with photon energy, and Resonant Auger peaks that are stationary in kinetic energy. On deuteration of these molecules, some of these peaks change intensity significantly. This is the signature that they are due to decay of oxygen 1s excited methoxy (CH3O*) and formlyoxyl radicals (HCO2). The bond to the acid hydrogen in each case is broken before the core decay, and deuteration slows this process, so that core decay occurs before dissociation. In contrast, for dimethyl ether (structurally related to methanol, but lacking an acid hydrogen) no evidence of ultrafast dissociation was found. For these molecules, the whole valence band resonates and not just the symmetry allowed states, suggesting that vibronic coupling is significant. Formaldehyde has also been studied for O 1s to carbonyl pi resonance excitation. As in previous work at the carbon edge, the highest occupied molecular orbital does not resonate, but the intensity of the second highest orbital is resonantly enhanced.

66

Incorporation and site preference of Sc in garnets: the join pyrope-grossular

Simona Quartieri1, Maria Chiara Dalconi2, Roberta Oberti3,

Federico Boscherini4, Gianluca Iezzi5, Massimo Boiocchi6

1Dip. di Scienze della Terra, Salita Sperone 31, 98166 Messina S. Agata, Italy e-mail: simonaq@unimo.it

2Dip. di Scienze della Terra, C.so Ercole I° d’Este, 44100 Ferrara, Italy 3CNR, Istituto di Geoscienze e Georisorse, via Ferrata 1, 27100 Pavia, Italy

4INFM and Dip. di Fisica, Viale Berti Pichat 6/2, 40127 Bologna, Italy. 5Dip. di Scienze della Terra, via dei Vestini 30, 66013 Chieti Scalo, Italy

6Centro Grandi Strumenti, via Bassi 21, 27100 Pavia, Italy Incorporation and site preference of Sc (~ 5%) in four synthetic garnet compositions (Py, Py60Gr40, Py20Gr80, and Gr) along the join pyrope-grossular were investigated by a multi-disciplinary experimental–theoretical approach, which combines EMPA, single-crystal and powder XRD, and Sc K-edge XAFS. The XAFS experiments were performed at ID26(ESRF). The XANES spectra clearly show significant differences in the spectral features of grossular and pyrope, suggesting different local environments for Sc. A multi-shell fit of the EXAFS signals shows that Sc is incorporated into the dodecahedral X site in the pyrope-type structure, but mainly in the octahedral Y site in the grossular-type structure. Investigation of the solid-solution terms showed distinct site-partitioning behaviours for Sc. The first shells contributions of the Py60Gr40 EXAFS signal could be obtained by a weighted combination of Sc in both the tetrahedral (T) and the X site, whereas that of the Py20Gr80 EXAFS signal could be fitted by a weighted combination of single scattering paths calculated for Sc in both the Y and the T site. In this latter case, however, a minor occurrence of Sc at the X site cannot be ruled out. These results are fully compatible with those of the structure refinement of the end-members, which showed (i) higher site-scattering (ss) and adp values at the X site and lower ss at T in Py; (ii) higher ss and longer mbl at Y (and T) in Gr. The site partitioning and preference of Sc in garnets is thus dramatically determined by the matrix.

67

Adsorption of thiophene on a Si(001)- 2××××1 surface studied by photoelectron spectroscopy and diffraction

M. Shimomura1, Y. Iejima2, K. Yajima 2, T. Yagi2, T. Goto2,

R. Gunnella2,3, T. Abukawa2, Y. Fukuda1, and S. Kono2

1Research Institute of Electronics, Shizuoka Univ., Johoku, Hamamatsu 432-8011, Japan

2Institute of Multidisciplinary Research for Advanced Materials, Tohoku Univ., Katahira, Aoba-ku, Sendai 980-8577, Japan

3UdR INFM, Dept. of Phys., Univ. of Camerino, Camerino 62032, Italy

Chemisorption of thiophene on a Si(001) surface has been studied by synchrotron radiation induced photoelectron spectroscopy (SRPES). Two adsorption-related components in Si 2p and S 2p spectra are observed after exposure of thiophene. It is suggested that the two components of Si 2p are ascribed to silicon bonded to hydrocarbon and sulfur. The core-level shift resolved photoelectron diffraction (PED) result indicates that the low-kinetic-energy component of S 2p can be ascribed to 2,5-dihydrothiophehe-like species. Another S 2p component could be assigned to dissociated sulfur based on the results of PED and time evolution of the spectrum under irradiation. These assignments are consistent with the core-level shift of S 2p.

68

Size-dependent oxidation in iron/iron oxide core-shell nanoparticles: an X-ray absorption study at the Fe and O

edges

L. Signorini1, E. Bonetti1, F. Boscherini1, L. Pasquini1

1 Dip.. di Fisica, Università di Bologna The iron-iron oxide system is certainly one of the most studied materials in the class of the core-shell nanoparticles [1,2] because of its peculiar magnetic and magnetoresistive properties [3,4]. Although these properties are strictly linked to the features of the oxide shell, little is known and discrepancies have been reported concerning its local structure, usually pictured as a mixture of magnetite (Fe3O4) and maghemite (γ-Fe2O3), i.e., the two iron oxides with a spinel structure. In our study [5] we report a detailed morphological and structural characterization of iron/iron oxide core-shell nanoparticles using X-ray Absorption Fine Structure (XAFS) spectroscopy performed at both the Fe- and the O-K edges. Complementary information was obtained using XRD. XAFS was able to distinguish and quantify the two different oxide contents, providing, a complete structural picture of iron-iron oxide core shell system. Besides, size/structure correlation has been found and explained in terms of morphological and structural disorder arguments. Core shell nanoparticles with core size ranging from 7 to 21 nm were synthesized using an inert gas condensation technique [6] followed by 12 hours of controlled surface oxidation. Rietveld analysis of diffraction patterns shows the presence of α-Fe nanoparticles surrounded by a 2-3 nm thick oxide layer with a disordered cubic spinel structure. A clear shift of the absorption threshold position in the O XANES spectra allowed us to calculate the volume concentration of the two different oxides, while a complete structural characterization of the heavily disordered spinel structure was performed fitting both the series of EXAFS spectra with the ab-initio calculation of all significant contributions to the absorption cross-section. XAFS measurements showed size-dependent changes in the local structure and oxidation state of the oxide shell, in particular, maghemite fraction increases at the expense of magnetite as the core dimensions decrease. This behavior can be explained in this way: for temperature lower than 450 C,° γ-Fe2O3 is the most stable iron oxide and, in presence of oxygen, Fe3O4 will spontaneously transform in maghemite increasing its concentration. This process is mediated by cations and vacancies diffusion into the particle. Due to the reduced radius of curvature, the oxide layer of smaller particles is expected to exhibit a higher degree of structural disorder and lower coincidence interfaces between crystallites. These features enhance the diffusion of vacancies and Fe cations, thus speeding up the rate of the magnetite-to-maghemite transformation. From the technological point of view, the observation of this size-dependent oxidation in iron-iron oxide core-shell particles could pave the way for the possibility of tuning their electronic transport and magnetic properties.

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References [1] - K. Haneda and A. H. Morrish, Nature (London) 282, 186 (1979). [2] - S. Gangopadhyay, G. C. Hadjipanayis et al. Phys. Rev. B 45, 9778 (1992). [3] - L. Del Bianco, D. Fiorani, E. Bonetti et al. Phys. Rev. B 66, 174418 (2002). [4] - L. Savini, E. Bonetti, L. Signorini et al. J. Magn. Magn. Mater. 262, 56 (2003). [5] - L. Signorini, L. Pasquini, F. Boscherini et al Phys. Rev. B 68, 195423 (2003). [6] - C. G Granqvist and R. A. Buhrman, J. Appl. Phys. 47, 2200 (1976).

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Indice Analitico

72

A Abbas, 50 Abukawa, 27, 67 Alagia, 23, 38, 39 Alberti , 38 Annese, 40 Antonangeli, 41 Aquilanti , 61 Aracne, 41 Armellini , 46 Artioli , 29 Avaldi , 39

B Badro, 41 Balerna, 20 Bardelli , 42, 56, 62 Barla, 33 Bartynski , 21 Battocchio, 34, 63 Bellatreccia, 47 Benedetti, 45 Benfatto, 62 Berakdar, 26 Berlier , 36 Bertoni, 52 Boiocchi, 66 Bolognesi, 60 Bonetti, 33, 68 Borgatti , 34, 44, 63 Boscherini, 24, 45, 46, 55, 57, 66, 68 Braicovich, 40 Brigatti , 11 Brookes, 40 Bucar, 64 Burattini , 30

C Calvani, 30 Carboni, 46, 55 Carpenè, 24 Carravetta, 28, 63 Cautero, 31 Cerulli , 29 Cestelli Guidi, 30 Cibin, 47 Cipriani , 54 Colonna, 45 Continenza, 32 Contini , 38, 48 Coreno, 22, 39, 64, 65 Cumakov, 33

D D’Acapito , 36, 57 D’Addato , 55 Da Pieve, 21, 26 Dalba, 49 Dalconi, 66 Davoli, 50 De Fanis, 28 De Panfilis, 54, 61 de Simone, 22, 39, 64, 65

Decleva, 38 Della Ventura, 47 Deriu, 33 Dettin, 63 Di Cicco, 10, 35, 61 Di Trolio , 51 Diab, 49 Dimoulas, 57 Doyle, 34, 44, 63

E Evangelista, 23

F Fanciulli , 57 Farber, 41 Farges, 12 Farrokhpour , 65 Ferriani , 52 Fiorani , 51 Fiori , 50 Fiquet, 41 Fondacaro, 31 Francia, 24 Fratoddi , 34 Fronzoni, 38 Fukuda, 67 Funakoshi, 17

G Ghiringhelli , 40 Giachini, 24 Giglia, 34, 44, 63 Giuli , 25, 54 Goto, 67 Gotter, 21, 26 Green, 22 Grioni , 31 Groppo, 55 Gunnella, 27, 67

H Hiraya , 28 Hjelte, 28

I Ibrahim , 50 Iejima , 67 Iezzi, 66 Iucci, 63

J Jones, 22

K Karlsson, 28 Kitajima , 28 Kono, 27, 67 Koyano, 28 Krastanov, 31

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Krisch, 41

L Lacovig, 31 Lamberti , 36, 55 Larciprete , 51 Leoni, 60 Leupold, 33 Liberati , 45 Liebske, 17 Liscio, 56 Longo, 20 Luches, 45, 55 Lupi , 30

M Mahne, 34, 44, 63 Malferrari , 11 Mallardi , 24 Malvestuto, 46, 57 Manju , 62 Marcelli , 30 Marri , 59 Martorana , 20 Mavrou , 57 McGrady, 22 Medici, 11 Meneghini, 42, 49, 56, 62 Merlini , 29 Milani , 60 Minicucci , 35, 61 Mobilio , 42, 56, 62 Monaco, 31 Monesi, 62 Morgante, 21 Mottana, 13, 47 Munakata, 27 Mungall , 25

N Nannarone, 34, 44, 63 Nucara, 30

O Oberti , 66 Occelli, 41 Offi , 21, 26, 31 Ohtani, 17 Orlanducci, 50 Ottaviano, 32

P Palazzo, 24 Panaccione, 31 Paolicelli, 31 Paris, 25, 54 Parisi, 51 Pasquini, 33, 68 Passacantando, 32 Pavese, 15 Pedio, 34, 44, 63 Piancastelli, 28 Piccinini, 30

Picozzi, 32 Pilosio, 39 Pittana, 31 Poe, 17 Polzonetti, 34, 63 Poppi, 11 Pratesi, 35, 54 Prestianni, 20 Prestipino, 36, 55 Prince, 39, 64, 65 Priolo, 32 Pritchard , 22 Profeta, 32 Pronin, 45 Prosperi, 38, 48

Q Quartieri , 66

R Requardt, 41 Richter, 39, 64, 65 Rocca, 46, 49 Rocci, 35, 61 Romano, 17 Rubie, 17 Rüffer , 33 Ruocco, 21, 23, 26 Russo, 34

S Sacchi, 31 Saito, 28 Sarma, 42, 56, 62 Sessa, 50 Shimomura, 27, 67 Signorini, 68 Spiga, 57 Spoto, 36 Stefani, 21, 23, 26, 31 Stener, 38 Stranges, 23, 38, 39 Sugata Ray, 42, 56 Suzuki, 17 Svensson, 28

T Tabrizchi , 65 Tagliaferri , 40 Takano, 27 Tanaka, 28 Terasaki, 17 Terranova, 50 Testa, 51 Tommasini, 31 Torelli , 31 Trapananti, 61 Turchini , 38, 48, 51

U Ueda, 28

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V Valeri , 45, 55 Vellianitis , 57 Venturoli , 24

W Wu, 50, 54

Y Yagi, 67 Yajima , 67

Yamazaki, 27 Yao, 21 Yoshida, 28

Z Zecchina, 36 Zema, 38, 48, 51 Zhong, 50 Zitnik , 64