Issue Number 26

Editor–Sue Free. Cambridge University Chemistry Dept, Lensfield Road, Cambridge, CB2 1EW, UK.Tel/Fax +44 1223 336536. Email-SJF1000@cus.cam.ac.uk. Web Page containing contact list andother announcements – http://www.phchem.uni-essen.de/gsd/

GAS SURFACE NEWS

December 1999

I N S I D E T H I S I S S U E

2 Research Reports- Leiden Inst of Chemistry, University of Leiden (Mischa Bonn, Prof. Dr Aart Kleyn)

4 Current Research - L.I.S.E. Facultés Universitaires Notre-Dame de la Paix in Namur (Petra Rudolf)

9 Meeting Reports

15 Papers for Publication

17 Job Vacancies and Announcements

23 Diary Page

24 Continuation from Page 1 and Reply Slip – EVERYONE MUST REPLY TO CONTINUE SUBSCRIPTION

GSDList andWeb PageThis issue of theNewsletter is also availableon the Web site. To testyour ability to read andd o w n l o a d c h e c khttp://www.phchem.uni-essen.de/gsd/ You willneed Adobe AcrobatReader (you can downloadthis free from the AdobeWeb site – Version 4 ispreferable)).

Gas-Surface DynamicsEmail Server - available toall those on the Gas-Surface News Mailing list.Just send your message toGSDList@phchem.uni-essen.de.

Editors NoteThank you to all those who replied to the survey earlier this year on thefuture of Gas-Surface News. We have received enough support to suggestthat publishing on the Web would be viable so this is the last issue postedout to the entire address list. We will continue with the policy of askingInstitutes to pay subscriptions so that all in that Institute who are interestedmay have access to GSNews at no extra charge. This policy also allowsvery small groups and individuals who are not part of a group, to receive theNewsletter free. In order to spread the costs fairly, however, it is stillimportant to increase our subscriptions base. We hope more Institutes willbe able to pay, we will increase the subscription from £50 to £60 (firstincrease in 4 years) and we will take efforts to reduce our costs. On theback page you will find a list of all the Institutes already paying annualsubscriptions. If your own institute is not amongst them, you are asked toconsider whether they could be added. If the list is not extended, we will beunable to cover our costs.

As part of this increased efficiency I propose to completely re-draw theaddress list and GSDList (Email Server). After 9 years there are manyaddresses that are no longer correct. EVERYONE is asked to complete theREPLY SLIP ON THE BACK PAGE and return it (via post or email) tomyself. If you do not have access to the Web, please remember to tick thebox to receive a copy by post.

I look forward to hearing from you all and meanwhile – enjoy this issue andplease invite any new members of your group to join the mailing list. Thenext issue is planned for early April. (Continued on back page....)

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Research Report

Very Small and Very Fast: Studies of Surface Structure andDynamics

Leiden Institute of Chemistry, Leiden UniversityP.O. Box 9502, 2300 RA LEIDEN

The Netherlands

With the move of Aart Kleyn from the FOM-Institute in Amsterdam to head the “Surface andCatalysis” Group at the Leiden Institute ofChemistry in Leiden, the scope of the researchthere has broadened considerably. It was, ofcourse, quite broad to begin with: BenNieuwenhuys has supervised, for many years, agroup doing research focused on both supportedcatalysts, -real catalysts in reactors -and on surfacescience investigations on model catalytic systems.Present topics include "non-linear processes onsurfaces, STM investigations of multicomponentsurfaces and catalytic oxidation reactions onmulticomponent catalysts. A recent overview waspresented in GSN 18 {April 1997}. Aart is nowfurther introducing molecular beams into theLeiden Group.

What is more, with Aart’s arrival in Leiden, anamplified femtosecond (1 fs = 10-15 s) lasersystem, which was being used in Leiden for thestudy of ultrafast processes in liquids, becameavailable for experiments on surfaces due to theretirement of a senior staff member of aneighboring group. Aart then asked theundersigned, at that time working as a post-doc inthe group of Martin Wolf with Prof. Ertl at theFritz-Haber-Institute in Berlin, to join his group inLeiden to set up a new experiment to investigatethe dynamics of surface reactions directly bymeans of time-resolved surface spectroscopy. Ihave already been working on that type ofexperiment in Berlin.

Ahmed Zewail, at the California Institute ofTechnology recently won the Nobel in Chemistryfor his ground-breaking work using femtosecondlasers to investigate chemical reaction dynamics.Zewail and co-workers were the first todemonstrate the possibility of real-timemonitoring the reactants turning into products as

the reaction is taking place. In these so-calledpump-probe experiments, one femtosecond laserpulse (pump pulse) is used to switch the reactionon, and a second (the probe pulse) is used toinvestigate changes in the electronic absorptionspectrum: The products exhibit different absorptionlines from the reactants, and the transition from oneto the other can be observed. Interestingly, onemakes use of the finite speed of light in suchexperiments: the probe pulse is guided over a mirrorthat can be moved back and forth. Increasing thepath length of the probe pulse by 1 µm causes adelay of 3.33 fs (speed of light: c = 3x108 m/s), sothat spectroscopic images of the system can betaken at pre-selected times, simply by moving thatmirror back and forth. The beautiful experiments byZewail and co-workers not only identified transitionstates and reaction intermediates for modelreactions, but also clarified the mechanism for someimportant chemical reactions. These experimentswere all carried out in the gas phase, in pulsedmolecular beams.

When one wants to transfer the same techniques toinvestigate the dynamics of reactions at surfaces,there are a few complicating factors. First of all, onehas to get a UHV system leak-tight andcharacterization equipment operative andsimultaneously get the femtosecond laser system towork. Anyone who has worked in either surfacescience or optics knows that to get one going is hardenough. Recent years, however, have seen a steadyincrease in the reliability of commercial lasersystems, and indeed, there have recently beenseveral studies successfully combining the two.

A second complication is that the electronic levelsare strongly smeared, shifted and broadened, whena molecule or atom is close to a metal surface. Thisis caused by the strong electronic coupling betweenthe electrons of the molecules on the surface and the

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metal electron gas. The absence of well-definedresonances makes it hard to investigate such asystem using electronic transitions in the visible orUV to probe the reaction dynamics. A thirdcomplication arises when one realizes that amonolayer of molecules at the surface is hard todetect optically, since it is optically very thin. Theoptical thickness of a system is defined as theabsorption cross section per sample unit lengthmultiplied by the sample thickness. It isimpossible to see changes in absorption due to thereaction when one sees no absorption to beginwith because there is only one layer of molecules.

The latter two problems can be overcome by thevery elegant technique of time-resolved Sum-Frequency-Generation (tr-SFG). The technique oftr-SFG is essentially femtosecond RAIRS(Reflection Absorption InfraRed Spectroscopy): Itallows one to record the vibrational spectrum ofadsorbates with very high sensitivity (signals fromcoverages below 10- 3 monolayers of CO havebeen observed) and very high time resolution(~100 fs). In analogy to the Zewail experiments,the surface reaction is switched on by a pumppulse, and the time evolution of the adsorbate isfollowed by means of time-resolved SFG. If wetake the desorption of NO from Ru(0001) as anexample of a simple surface reaction, we knowthat the frequency of the N-O stretch vibrationwill change from 1825 cm-1 at the surface to 1876cm-1 in the gas-phase. The temporal evolution ofthe vibrational frequency will give us informationon how long it takes for molecules to desorb, afterexcitation of the substrate. It has already beendemonstrated that important information onreaction dynamics and energy flow at surfaces canbe obtained from such experiments [1, 2],specifically with time-resolved (in that case:picosecond) SFG [3].

In Leiden, we initially plan to study simple,elementary surface reactions, such as thedesorption of NO from a metal surface. It shouldbe noted, however, that this research is not limitedto UHV: A very interesting trait of SFG is that, incontrast to RAIRS, it is specifically surface-sensitive. The vibrational signal can come fromthe surface only, so that the signal remainsuninfluenced by gas in front of the surface. It istherefore very well-suited for the study of(prototype) metal catalysts under ambientpressures and/or reactive conditions. This hasbeen demonstrated recently by Somorjai and Shen

(UCLA, Berkeley) for conventional (not time-resolved) SFG spectroscopy.[4] Time-resolved SFGcould provide an additional wealth of informationon catalytic systems under reactive conditions.

We have a few vacancies for PhD students andpost-docs for this project. Those who are interestedshould contact us.

Mischa Bonn

Leiden Institute of ChemistryLeiden UniversityP.O. Box 95022300 RA LEIDENThe Netherlandm.bonn@chem.leidenuniv.nl

[1] J.A. Prybyla, H.W.K. Tom and G.D. Aumiller,Phys. Rev. Lett. 68, 503 (1992).[2] M. Bonn, S. Funk, Ch. Hess, D. N. Denzler, C.Stampfl, M. Scheffler, M. Wolf and G. Ertl, Science285, 1042 (1999).[3] A. Bandara, J. Kubota, K. Onda, A. Wada, S.S.Kano, K. Domen and C. Hirose, J. Phys. Chem. B102, 5951 (1998).[4] X. Su, P.S. Cremer, Y.R. Shen and G.A.Somorjai, Phys. Rev. Lett. 68, 503 (1992).

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Laboratoire Interdisciplinaire de Spectroscopy Electronique, (LISE)

Facultés Universitaires Notre-Dame de la Paix,Rue de Bruxelles 61, B-5000 Namur, Belgium

By Petra Rudolf

The group of currently 2 Ph.D. students (Ingrid Marenne and Francesca Cecchet), 3 postdoctoral researchers(Annette Wingen, Celine De Nadaï and Caroline Whelan), and a lecturer (Petra Rudolf) is involved the studyof the vibrational and electronic properties of new carbon-based materials such as fullerenes and carbonnanotubes and of thin film of supramolecular assemblies such as catenanes and rotaxanes. We have becomean all-female group only very recently, when Charles-André Fustin and Michael R. C. Hunt finished theirrespective Ph.D and postdoctoral researcher appointments. We are part of a rather large surface sciencelaboratory, the Laboratoire Interdisciplinaire de Spectroscopy Electronique or LISE, consisting of fourprofessors, two in physics and two in chemistry, five permanent scientific staff, 4 technical staff, 7postdoctoral researchers, 9 phd students and a variable number of graduate students.

Introduction on the LISE

Capitalising on 25 years experience with electronspectroscopies (XPS-ESCA, HREELS, AES,UPS, and synchrotron radiation), and electrondiffraction, the LISE's research projects cover thepreparation, modification and characterisation ofsurfaces and interfaces. Some fundamental goalsare the determination of elemental compositionand crystallographic structure of the surface, theidentification of the chemical bonds, theconcentration profiles of elements at an interface,and the composition maps at a surface (with alateral resolution of 10 µm).

Many research projects carried out at the LISE,which I do not detail here, are chosen in view ofpossible future applications, and some alsocomprise the behaviour of surfaces or thin filmsunder laser, ion and plasma irradiation. Particularemphasis is laid on microelectronics(semiconductors, superlattices, includingsuperconductors and heterostructures), structuralmaterials (ceramics, polymers, including carbonfibres, composites and biopolymers), and catalysts(car exhaust cleanup). The LISE specialises in thepreparation and characterisation of interfacesbetween these materials and typical metal/ semi-

conductor/ ceramic /organic layer combinationsare explored.

Most techniques available at the LISE are electronspectroscopies. Recently added techniques areSTM/AFM (UHV), FT-IR, FT-Raman and UV-Vis spectroscopies. An important newdevelopment at the LISE in the past two years wasthe set-up of an electrochemistry laboratory.

In addition, the LISE is active in designing andbuilding electron spectrometers (MilliScan andCDEELS). Furthermore integrated systems havebeen built for fabrication, treatment and analysisof materials under UHV conditions (IntegratedUHV Thin Films System, Plasma TreatmentDevice, etc.). Moreover, several softwares havebeen developed for instrument control, dataacquisition and data treatment.

The LISE is a member of the Institute for Studiesin Interface Sciences (ISIS) of the FUNDP andmany international networks, and is involved injoint research projects with other laboratories inacademia and industry.

The large concentration of people working in theISIS, both theoretically and experimentally, and

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the great variety of analytical tools available makeNamur an exciting place to do Surface Science.For further information on activities of the other

groups the interested reader is referred to the LISEWebPageshttp://www.fundp.ac.be/~lise .

Figure 1: C1s photoemission spectra for1 ML C6 0 on Ni(110), Pt(111) andAg(111) and for a thick C60 filmdeposited on Ni(110). The right panelshows an enlargement of the shake-upregion for the same samples

Research on Fullerenes

The study of interactions between fullerenes andsurfaces has developed into a major area of re-search on this third allotropic form of carbon. Twoaspects motivate this interest: firstly, from atechnological point of view, the substrate-inducedmodification of the electronic and structuralproperties of C60 layers is an important question tobe addressed if this new material is to find anapplication in the electronics industry. Secondly,the variety of both bond strength and bondcharacter observed in the interaction between C60

and a substrate is exceptional and still far frombeing completely understood from a fundamentalpoint of view. The bond which this moleculeforms with a substrate can be of very weak vander Waals type on surfaces such as for exampleGeS,i or result in a very strong charge transfer ofup to 11 electrons/molecule when adsorbed on Kmultilayers.ii On all metallic surfaces investigatedso far,iii,iv fullerenes are chemisorbed, but thedegree of hybridisation of the C60 molecularorbitals with the substrate electronic states and theamount of charge transfer differs greatly fromsubstrate to substrate as illustrated also by the C1sphotoemission spectra shown in figure 1.

Depending on the system in question, theincreases in the C 1s width above that of themultilayer in principle reflect the followingeffects: C atomic sites with significantly differentenvironments; creation of electron-hole pairs;coupling to the charge carrier plasmon. The lattertwo are dominant in cases involving significantcharge transfer, such as C60/Ag(111), for whichEELS data show a high intensity of low-energyelectronic excitations and the charge carrierplasmon at 0.9 eV. We note that in the C 1slineshape the coupling to the charge carrierplasmon is difficult to resolve. Typical for thecovalently bound MLs in which little or no chargetransfer occurs (such as C60/Pt(111) shown here)are narrow C 1s lines. This observation tends torule out a significant role for inequivalent C sites,which can be tentatively explained by the veryefficient intramolecular screening of local charges.A further source of information is the shake-upstructure, blown up in the right panel of Fig. 1.This structure corresponds to coreionised finalstates in which a valence electron is promotedfrom an occupied to an unoccupied level and istherefore similar to a convolution of the occupiedand unoccupied parts of the valence band. Thebroadening of the shake-up structures in the other

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ML films can be regarded as a measure for thebonding interaction with the substrate.

These changes brought upon the electronicstructure of the molecule by adsorption haveimportant consequences for the thermal stabilityof adsorbed fullerenes.v, vi While all coverages ontop of the first physical monolayer of C60 do notinteract with the substrate and therefore all start todesorb at about 455 K, the first layer can eitherdesorb at slightly higher temperature as onAg(111), or decompose as on Pt(111) or Ni(110)in a kinetically limited process. We have shownthat this destruction occurs via conversion of arelatively weakly bound state arising from roomtemperature adsorption into a strongly bound statein competition with .

Molecular desorption. On Mo(110) a progressionthrough 4 distinct chemisorbed states is observed,from weakly bound through the immediateprecursor to fragmentation, with increasinghybridisation between molecule and substrate.vi

Figure 2: Infrared spectra in the 400-2500 cm-1 region of aCu(100) surface collected during C60 deposition at roomtemperature. A broadband reflectance change as well as oneabsorption band at 1440 cm-1 are clearly seen.

Another very interesting aspect of surface sciencewith fullerenes is a surprisingly rich scenario forthe vibrational dynamics of chemisorbed C60. OurInfrared spectroscopy studies with synchrotronradiationvii of C6 0 on Ag(111), Au(110) and

Cu(100) reveal that a non-IR active modebecomes active upon adsorption and that itsfrequency shifts proportionally to the chargetransferred from the metal to the molecule byabout 5cm-1 per electron. Additionally, as shownin figure 2, the adsorption is accompanied by abroadband reflectance change which is interpretedas due to the scattering of conduction electrons ofthe metal surface by the adsorbate. The reflectancechange allows the determination of the frictioncoefficient of the C6 0 molecules which is rathersmall (corresponding to an inverse lifetime of thefrustrated translation of the adsorbate due tocreation of electron-hole pairs τ ~ 102 ps),consistent with a marked metallic character of theadsorbed molecules.

Currently we are exploring the interaction of het-erofullerenes such as C59N and of endofullerenessuch as Sc2@C84 with metal surfaces.

Research on Catenanes and RotaxanesIn recent years, new synthetic developments havemade possible the preparation of molecules withnon trivial architectures and topologies. Catenanesin which two macrocycles are threaded like therings of a chain and rotaxanes in which amacrocycle is threaded onto a bar with stoppers atboth ends, by right belong to this arena and havebeen the focus of a concerted effort carried out bymany important laboratories world wide. Thefundamental question arising from the newlyacquired synthetic capabilities is whether thesespecies, either as a class or individually, can havean impact in the real world as parts of deviceswhose design and construction would not beaccomplished without their exploitation. Severalof the interlocked structures prepared so far canindeed change the relative positions of theircomponent parts under external stimulus: themacrocycles of the catenane can circumrotate oneanother like the rings of a macroscopic chain, themacrocycle of a rotaxane can change positionalong the bar and this adds a degree of freedomnot available to other systems. To date elegant andincisive work has been performed with the intent

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of characterising various types of catenanes androtaxanes. However, in its near totality, it wascarried out in solution and only a very smallfraction of effort was concerned with the solidstate properties. In our work we try to bridge hefundamental gap due to the lack of solid statecharacterisation, which is the first mandatory steptowards real applications. The molecules we workon are synthesised by D. A. Leigh and his group atthe Cent re for Supramolecular andMacromolecular Chemistry of the University ofWarwick, U.K.. For the interpretation of ourresults we closely collaborate with F. Zerbetto andhis group at the Department of Chemistry ‘G.Ciamician’ of the University of Bologna, Italywho carry out theoretical studies on these systems.

We started out with the characterisation of thevibrational properties of the simplest benzylicamide [2] catenane by infrared spectroscopyviii: thevery nature of the molecule - in which severalsimilar groups interact either via bonds or viaspace - results in a system with a high sensitivityto the environment which is typical of thecatenane only and is not present in the parentmacrocycle. We then carried out studies of thelow-lying electronic states of the same moleculeix

giving support to the theoretical picture whichshows that partial delocalisation of the electronic

states over the many chromophores of thecatenane can occur.

From there we moved on to the thin-film growthof this catenane. The molecules were depositedonto gold single crystals by sublimation underUHV or by dipping the substrate into a solution ofthe catenane. Sublimation yielded well-orderedfilms (albeit with domain diameters of only about100 Å) while dipping produced only disorderedfilms.x The vibrational spectra acquired byHREELS indicated that the first layer of catenanesis chemisorbed. This result, confirmed by XPSdata,xi implies that the macrocycles are immo-bilized on the surface and that the “mechanicalbond” which holds them together is no longerdynamic.

Of interest for possible applicational aspects istherefore the development of techniques to growtwo dimensional ordered arrays of catenanes androtaxanes such that these molecules are still ableto move. In a recent study we report our firstattempts in this directionxii: the characterisation ofthiol-terminated catenane and rotaxane thin filmsself-assembled from the liquid phase on Au(111)using HREELS and XPS. The HREELS studyshown in f igure 3 has revealed

Figure 3: HREELS spectra collectedin specular (θi = θr = 45°) and off-specular (θi = 45°, θ r = 25°)scattering geometries at a primarybeam energy of 6.0 eV from thiol-terminated GlyGly rotaxane, GlyGlythread and benzylic amide[2]catenane (a) adsorbed at 300 K onAu(111) and (b) following annealingof the layers for 45, 45 and 120minutes at ~500 K, respectively.Typical energy resolution of theelastic peak was 80-160 cm- 1 interms of the full width halfmaximum.

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the absence of a preferred molecular orientationfor rotaxane and catenane adlayers at roomtemperature which can be explained by thecomplex structure of such molecules. Only thecatenane which is di-thiol terminated seems toform some domains but without any long rangeorder. XPS results have confirmed the occurrenceof thiolate formation for each molecule. Self-assembly of di-thiol terminated catenane follow-ing 14 hours immersion results in the formation ofa monolayer of molecules oriented principallyparallel, as obtained in case of sublimatedcatenane on gold, and not perpendicular to thesurface. The study of the effects of annealing

indicates the formation of larger domains with achemisorption via the carbonyl on the gold surfacein the case of rotaxane and catenane. Variations insulfur 2p signal intensities revealed molecularrearrangement resulting in a tilt of the molecules,favoured by partial desorption, to the extent that aflat-lying configuration becomes probable. Basedon these first results, the catenane looks promisingfor the development of novel self-assembledmonolayers in contrast with the rotaxane. Furtherexperiments are in progress in order to determinethe optimum experimental conditions to obtainmore ordered monolayers.

REFERENCES

i G. Gensterblum, K. Hevesi, B. Y. Han, L. M. Yu, J.-J. Pireaux, P. A. Thiry, R. Caudano, A. A. Lucas, D. Bernaerts, S.Amelincks, G.VanTendeloo, G.Bendele, T.Buslaps, R.L.Johnson, M.Foss, R.Feidenhans’l and G.Le Lay., “Growth mode andelectronic structure of the epitaxial C60(111)/GeS(001) interface”, Phys. Rev. B50 (1994) 11981. ii A. J. Maxwell, P. A. Brühwiler, S. Andersson, N. Mårtensson, and P. Rudolf, “Electronic Structure of KXC60 compounds withx>6”, Chem. Phys. Lett. 247 (1995) 257.iii P. Rudolf, M. Golden, and P. A. Brühwiler, "Studies of Fullerenes by the Excitation, Emission, and Scattering of Electrons", J.Elect. Spec. and Rel. Phen. 100 (1999) 409. iv P. Rudolf, " C60 adsorption on metal surfaces" invited review paper in Electronic Properties of Novel Materials: Fullerenes andFullerene Nanostructures, eds. H. Kuzmany, J. Fink, M. Mehring, and S. Roth, World Scientific Publishing Co. Ltd., Singapore(1996) p.263. v M. Pedio, K. Hevesi, N. Zema, M. Capozi, P. Perfetti, R. Gouttebaron, J.-J. Pireaux, R. Caudano and P. Rudolf, " C60/metalsurfaces: Adsorption and Decomposition", Surf. Sci. 437 (1999) 249. vi M. R. C. Hunt, A. Rajogopal, R. Caudano and P. Rudolf, "Temperature-dependent chemisorption of C60 on Mo(110): Precursorsto cage destruction", Surf. Sci., in press. vii P. Dumas, M. Hein, A. Otto, B. N. J. Persson, P. Rudolf, R. Raval and G. P. Williams, "Friction of molecules on metallicsurfaces: experimental approach using synchrotron infrared spectroscopy", Surf. Sci. 433-435 (1999) 797. viii M. Fanti, C. A. Fustin, D. A. Leigh, A. Murphy, P. Rudolf, R. Caudano, R. Zamboni and F. Zerbetto, "The high-frequencyvibrations of the simplest benzylic amide [2]catenane", J. Phys. Chem. A109 (1998) 5782-5788. ix A. M. Brouwer, W. J. Buma, R. Caudano, M. Fanti, C.-A. Fustin, D. A. Leigh, A. Murphy, P. Rudolf, F. Zerbetto, J. M. Zwier,"Experimental and theoretical studies of the low-lying electronic states of the simplest benzylic amide [2]catenane", Chem. Phys.238 (1998) 421. x C. A. Fustin, P. Rudolf, A. F. Taminiaux, F. Zerbetto, D. A. Leigh and R. Caudano,"Growth and Characterisation of BenzylicAmide [2]Catenane Thin Films", Thin Solid Films 327-329 (1998) 321. xi C. A. Fustin, R. Gouttebaron, P. Rudolf, F. Zerbetto, D. A. Leigh, and R. Caudano, "Photoemission Study of Benzylic Amide[2]Catenane Films, Influence of Potassium Intercalation", submitted. xii C. De Nadaï, C. M. Whelan, C. Perollier, G. Clarkson, D. A. Leigh, R. Caudano and P. Rudolf, "The self-assembly ofmechanically interlocked and threaded rings: A HREELS and XPS study of thiol-functionalised catenane and rotaxane moleculeson Au(111) ", Surf. Sci. in press.

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Meeting Report – Euro-Conference

“Elementary steps in fast catalytic oxidation reactions”Hotel Mercure, Lelystad, Flevoland, NL - October 2-6 1999

Heterogeneous catalysis is of great importance for the(petro) chemical industry. Practically all the chemicalprocesses are steered by catalysts. Most of theindustrially used catalysts have been developed viaempirical knowledge and 'trial and error' experimentsduring the past 80 years. More stringent environmentallegislations or the demand for a more efficient use ofthe feedstock continuously requires improved/newcatalysts. This, however, is not an easy task, sinceheterogeneously catalysed reactions are extremelycomplex. Basic research is needed to develop taylor-made catalysts.

In the past 20 years, our basic insight into gas-surfaceinteractions has improved tremendously. This insighthas been obtained by the study of well defined modelsystems. The complexity of these model systems hasincreased, thus decreasing the gap between surfacescience and industrial catalysis. It is, therefore,anticipated that in the coming decade the role ofsurface science in the development of heterogeneouscatalysis will become more important.

Topics of the conference: a) Fundamental studies onadsorption and reactions on surfaces related tooxidation catalysis.b) Oxidation catalysis.

The subject of this workshop was 'elementary stepsin fast catalytic oxidation reactions'. Much researchis done to improve existing (for example, etheneepoxidation) and to develop new processes (forexample, catalytic conversion of methane to synthesisgas). In addition to partial oxidation reactions, totalcatalytic oxidation is of great importance to protectionof the environment (for example, automotive catalysis).Much fundamental research on the dynamics of relatedsystems is done in Europe at several universities andnational laboratories.

The purpose of the workshop was to stimulatecontacts between researchers in the fields of surfacescience and applied heterogeneous catalysis.

Venue: Hotel Mercure Lelystad, located in the new

town Lelystad, a town built 30 years ago in the 'polder'Flevoland. Flevoland is the youngest part of theNetherlands and covers 225000 ha of new land whichwas part of the 'Zuiderzee'.

Organizing committee:

Bernard Nieuwenhuys (Leiden), chairmanGert-Jan Kramer (Shell, Amsterdam)

Bernd Riedmuller (Amolf, Amsterdam)Corine de Wolf (Leiden)

Dave King and Sue Free (Cambridge)Hella Knegtel (Leiden)

Total number of participants: 36 (7 women, and 29men), 8 with the Netherlands nationality, 7 with theGerman, 5 Greek, 3 British, 3 Italian, 3 Spanish, 2Danish, 1 Belgium, 1 Swedish, 1 Irish, 1 Finnish and 1with the Czech nationality. The Eu funds available forthis meeting were put to good use subsidizing most ofthe expenses for travel and accommodation for 26young scientists and, partly for 8 senior invited speakers.

Report

Surface science studies have provided a wealth ofinformation on the elementary steps in catalyticreactions. However, as was nicely shown by RobertSchlögl (FHI/Berlin) for partial oxidation reactions overCu and Ag, the active site cannot always be representedby single crystal model catalysts. Metastable structurescontaining the ’active site’ are formed under catalyticreaction conditions.

Ben Nieuwenhuys (Leiden) started with a briefintroduction on the topic of catalytic oxidation reactionson noble metal and transition metal oxide catalysts. Themajor part of his talk dealt with the question ‘how can theperformance of a noble metal catalyst in lowtemperature oxidation be improved’? It was shown thatthe combination of a noble metal with a transition metaloxide, in particular CuOx and MnOx, can yield very activecatalysts. Peter Thormählen (Göteborg) showed thatcatalysts based on Pt and CoOx, although exhibiting a

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very high activity in the individual reactions, deactivateunder real reaction conditions (Automotive catalysis).Another lecture dealing with noble metal-transitionmetal oxide catalyst was presented by BartZwijnenburg (Delft). It is a challenge to develop aprocess for the direct oxidation of propene to propeneepoxide. Bart showed that the epoxide is formed withlow yield but high selectivity from propene and H2 + O2

over Au/TiO2 catalystys. Ruud Grisel (Leiden)presented another talk dealing with oxidation reactionsover Au-metal oxide catalysts: a comparison of thebehaviour of these catalysts in CO and CH4 oxidation.

Phil Davies (Cardiff) presented STM results of O and Non Cu surfaces: formation of O + N islands, ‘mobile’Cu-O chains which ‘lock’ the surface preventingexpansion of the lattice needed for formation ofsubsurface O. O2 adsorption and dissociation on silversurfaces was the main topic of Aart Kleyn’s lecture(Leiden). The possible presence of physicallyadsorbed O2 and its relation to the weaklychemisorbed O2 (precursor for oxygen dissociation)were discussed. Costas Vayenas and DimitrosTsiplakides (Patras) discussed the origin ofelectrochemical promotion in catalysis and showedmany examples of electrochemical promotion inadsorption and catalytic reactions on metal surfaces:ethene oxidation to the epoxide and aldehyde. ThomasBär (Brussels) discussed the mechanism of NOdecomposition on silver and showed nice FIM imagesillustrating NO-induced structural changes of silver tips.FIM was also used by Thierry Visart de Bocarme(Brussels) to examine the catalytic oxygen-hydrogenreaction on Rh. Alessandro Baraldi (Trieste) discussedthe information that surface core level shifts canprovide on the first step of oxidation reactions:adsorption of oxygen. In particular the adsorption ofoxygen on Rh and Ru surfaces were discussed.Angelos Michaelides (Belfast) showed that DFT can beused to predict the catalytic reaction pathways forhydrogenation of C (CH, CH2, CH3, and CH4) and N(NH, NH2, NH3) and the reversed reactions.

Results of DFT slab calculations were also presentedby David King (Cambridge) for Co (1010) + CO + K.On the basis of these results a new model wasproposed for promoter action in heterogeneous

catalysis. Norbert Kruse (Brussels) discussed theformation of long chain alcohols from syngas over Cobased catalystys. In addition, the formation of nickelcarbonyl over various Ni surfaces was discussed. Theadsorption and dissociation of C2N2 on Rh(110) wasdiscussed by Federica Bondino (Trieste). Luca Rumiz(Trieste) discussed the adsorption of CO on Rh(111) onthe basis of time-resolved XPS studies with emphasis onthe population of CO adsorbed on atop and hollow sites.

A large number of talks were focused on the catalyticpartial oxidation (CPO) of methane. Bernd Riedmuller(Amsterdam) discussed the dissociative adsorption ofmethane on the stepped Pt(533) surface Gert JanKramer (Shell/Amsterdam) presented a nice overview ofthe present knowledge on CPO. Carlo de Smet(Eindhoven) discussed O assisted

CH4 dissociation and presented results of kineticmodelling of CPO on a Pt gauze catalyst in the presenceof transport phenomena. Ib Chorkendorff (Lyngby)discussed in detail the collaborative research of theDanish team concerning the elementary steps inmethane activation: molecular beam studies, STM andcalculations.

An excursion to the Shell and Technology Centre inAmsterdam was organized by Gert Jan Kramer: anoverview of research at Shell and a tour showingexperimental facilities. Herman Kuipers presented alecture on “New prospects for technology in Shell: CPO,fuel cells and the hydrogen future."

Overall this meeting represented the state of the art inthe subject elementary steps in fast catalytic oxidation.The attempt to bring together surface scientists,theoreticians and catalysis scientists was a greatsuccess and resulted in lively discussions.

Ben Nieuwenhuys, chairmanLeiden University

Leiden Institute of ChemistryP.O.Box 9502

2300 RA Leiden/The Netherlandsemail: b.nieuwe@chem.leidenuniv.nl

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Reactive Surfaces Symposium - 9-10th September 1999

Report by Stephen Jenkins (Department of Chemistry, Cambridge)

If a man may be judged by the quality of his friends, then surely a scientist must be judged by the quality of hisstudents, colleagues and collaborators. On the evidence of the attendance list for Professor David King's 60th birthdaysymposium on the 9th and 10th of September, his reputation as one of the world's leading surface scientists will besecure for many years to come.

Organised by one of Dave's former students, Professor Mike Bowker, the “Reactive Surfaces” meeting brought toCambridge a selection of delegates that would put many an international conference to shame; all linked by the factthat at some point or other their careers overlapped with Dave's. From Norman Sheppard, who gave Dave his firstlecturing job at the University of East Anglia in the late 60s, to the post-grads and post-docs of his current researchgroup, it seemed everybody had an anecdote to reveal, if not a colleague to embarrass.

The lectures themselves were an enlightening cross-section of surface science at the end of the 20th century, withsuch notables as John Yates and Bob Madix contribuing keynote addresses; the latter putting in an appearance asthe elusive mystery guest. Perhaps unsurprisingly, the King & Wells method for measuring sticking probability wasconsistently identified by many speakers as one of Dave's most outstanding and enduring contributions to the field.Unfortunately, pace precludes a more detailed report on the scientific content of a very varied and stimulatingmeeting.

Varied and stimulating would also be apt descriptions of the reception and dinner at Downing College, of which Daveis Master. The occasion brought a much appreciated opportunity for Dave's colleagues, past and present, to catch upon old friendships. For many in his current research group there was also the novelty of matching names known onlyfrom article by-lines to actual faces.

And so to the final day, on which Dietrich Menzel and Richard Lambert gave the keynote speeches. In the end,however, the only appropriate way to draw a meeting like this to a close was with a speech from the man himself, andDave duly obliged, wishing mainly to emphasise that the event should certainly not be seen as a swan-song. Watchthis space....

The “Reactive Surfaces” conference was sponsored by BP International, Elsevier Science, ICI Technology, JohnsonMatthey, Omicron Surface Science, Unilver Research and Vacuum Generators.

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European Research Conference on

Electronic Structure of Solids and Surfaces: Challenges inpredictive descriptions of reaction dynamics and growth properties

at surfacesLenggries (Bavaria), Germany, 18-23 September 1999

Chairperson: Axel Gross (TU Munich,)Vice-Chairpersons: Gianfranco Pacchioni (University of Milan)

Thorsten Kluener (FHI Berlin)

The theoretical description of reactions andgrowth properties at surfaces is an importantresearch field owing to its fundamental aspects aswell as its technological relevance. For apredictive description of processes at surfacesthe reliable determination of the interaction ofatoms and molecules with surfaces is aprerequisite. Due to the improvement of electronicstructure theory algorithms and the increase incomputer speed in the last years there has beentremendous progress in mapping out wholepotential energy surfaces for these processes.The main goal of this conference was therefore tobring together experts in the field of electronicstructure theory calculations with theoreticianswho work in the field of reaction dynamics andgrowth processes at surfaces. Morespecifically, the aim was to review the currentstatus of the field and to inspire fruitfulcollaborations between these two groups ofscientists which used to be rather separate in thepast. Equally important for the theoreticaltreatment of processes at surfaces is the closecontact to the experiment. Hence anothersignificant aspect of this conference was theparticipation of experimentalists working in thisfield.

To set the stage, the conference was opened witha session on fundamental aspects of electronicstructure calculations and density functionaltheory (DFT). The reliability of DFT calculations ismainly determined by the accurate treatment ofthe many-body effects. Axel D. Becke

(Queen's University, Kingston, Canada)discussed the construction of non-localexchange-correlation functionals. In theconstruction of these functionals there is stillsome variational freedom, a fact that was alsopointed out later in the conference by BjorkHammer (Aalborg University, Denmark). AxelBecke prefers to use this freedom to adjust asmall set of variational parameters in order toreproduce a set of known results, but there areother schools of thought that avoid to use anyadjustable parameters. Furthermore, theextension of DFT to treat polarizabilities andexcited states is of strong current interest. Twop o s s i b l e m e t h o d s , t i m e - d e p e n d e n tdensity functional theory and the GWapproximation were presented by Evert JanBaerends (Vrije Universiteit Amsterdam, TheNetherlands) and Rex Godby (University of York,UK), respectively. Although these methods canbe quite successful for small systems, thedetermination of electronically excited states forextended systems still represents a considerablechallenge.

DFT calculations only provide the potentialenergy for a set of discrete configurations. Indynamical simulations, however, a continuousrepresentation of the potential energy surface(PES) is needed. The talks of DougDoren (University of Delaware, USA) and HoriaMetiu (University of California at Santa Barbara,USA) were concerned with schemes for theinterpolation of ab initio energies. A neural

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network model for inter-atomic interactions waspresented by Doug Doren, while Horia Metiuintroduced a directed genetic programmingscheme for finding the best analytical fit to a setof given data. Both schemes are rathersuccessful in reproducing the PES for low-dimensional problems, however, their applicabilityfor problems with a large number of freedoms(say, more than 10) still has to be proven.

The sessions covering methods for theapplication of ab initio data to simulate processeson surfaces were opened by Geert-Jan Kroes(Leiden University, The Netherlands). He showedthat the benchmark system for the activateddissociation of molecules at surface - hydrogenon copper - can now be treated in a detailedmanner by s ix-d imensional quantumdynamics methods using a PES derived fromDFT calculations. These calculations allow aquantitative comparison with experiment so thatalso the accuracy of the DFT-derived PES can bechecked. Didier Lemoine (Universite de Lille,France) demonstrated the importance of the high-dimensionality in the simulation of scatteringprocesses by showing that the so-calledsupernumerary rotational rainbows which appearin low-dimensional simulat ion of NOscattering from Ag(111) disappear if also thesurface corrugation is considered.

The first talk in the session about growth andetching, corrosion and lubrication was given byHarald Brune (EPF Lausanne, Switzerland). Hereviewed the field of STM experiments to studynucleation and growth on homogeneous andinhomogeneous substrates. Due to the atomicresolution of the STM, these experiments canyield a detailed information about the microscopicprocesses, in particular if the experiments arecombined with ab initio calculations. Thetheoretical treatment of atomic growth processeswas the topic of the talk by Talat Rahman(Kansas State University, USA). She stressed theimportance of finite temperature effects in thesimulation of growth processes. For manysystems the fact what are the most favourableprocesses at a certain surface temperature is

determined by the Free Energy which includesentropic effects and not just by the bare barrierheights. This session was closed by the talk ofAnne Chaka (Lubrizol Corp., USA) with theprovocative title Quantum Mechanics and theAutomobile. She demonstrated that nowadaysDFT is already used by the chemical industry toilluminate the chemical processes underlying theperformance of lubricants and additives.

There is one main difference between chemicalreactions at surfaces and in the gas phase: atsurfaces energy can be very efficiently dissipatedby excitation of phonons or electron-hole pairswhile in the gas phase there are usually nodissipation channels open. However, thetheoretical treatment of dissipation, in particularwithin a quantum mechanical framework, stillrepresents a major computational challenge. Twocomplimentary approachs were discussed byRonnie Kosloff (Hebrew University, Jerusalem,Israel) and Shiwu Gao (Chalmers University,Gothenborg, Sweden). Ronnie Kosloff introduceda finite surrogate Hamiltonian to generate the trueshort time dynamics of a primary system coupledto a bath. Using the resurfacing of hydrogen to aNi surface he demonstrated the applicability ofthis approach if the temperatures are not toolarge and the time scales are not too long. ShiwuGao, on the other hand, presented a dissipativequantum dynamics method within the reduceddensity matrix formalism. This method, which candeal with high temperatures but is still restrictedto low dimensions, was applied to thephotoinduced reaction of oxygen on Pt(111). Analternative approach to determine reaction ratesin thermal equilibrium situations was presented byHannes Jonnson (University of Washington,Seattle, USA). He focused on quantum transitionstate theory in terms of Feynman path integralsand its application to hydrogen dissociativeadsorption.

As already mentioned above, the determination ofelectronically excited states still represents amajor challenge. But equally challenging is theinclusion of electronic transitions in the simulationof reaction dynamics. The semiclassical treatment

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of electronic transitions in molecular dynamicssimulations was the topic of the talk by John Tully(Yale University, New Haven, CT, USA), whilePeter Saalfrank (University College London, UK)presented a quantum mechanical description ofdesorption processes induced by electronictransitions. The semiclassical treatment caneasily be extended to higher dimensionsbut treats the electronic transition only in anapproximative manner. The quantum mechanicaldescription, on the other hand, can treat theelectronic transition properly, but is still limited tolow dimensions. The contact to experiment in thissession was provided by Katharina Al-Shamery(University Oldenburg, Germany) who gave adetailed report on laser induced desorptionexperiments from oxide surfaces.

Dave King (University of Cambridge, UK)presented molecular beam experiments ofimportant catalytic processes on Pt surfaces. Healso emphasized the important role that DFTcalculations can play in combination withexperimental results for a microscopicunderstanding of these processes. This wasfurthermore demonstrated in the talk by NotkerRoesch (Technical University Munich, Germany)who focused on oxide supported metal speciesinvestigated by DFT calculations using the clusterapproach to represent the surface. Bjork Hammer(Aalborg University, Denmark) showed that thereactivity at stepped surface can be enhanceddramatically compared to flat surfaces. Hedemonstrated how this enhanced reactivity canbe understood microscopically by carefullyanalyz ing DFT resul ts . As a l readymentioned above, he also pointed out that thereis an intrinsic uncertainty in the construction of theexchange-correlation functional in the generalizedgradient approximation which can lead tochanges of up to 0.3 eV in the barrier heights ofthe reactions he considered. The last talk of theconference was given by Mario Rocca (Universityof Genova, Italy) who showed experimentallyhow complicated the seemingly simple systemoxygen on Ag(100) can be.

The talks were supplemented by two postersessions. All posters were introduced by a three-minute, one-slide presentation which was wellreceived. The conference was closed byconcluding remarks of Volker Heine(Cavendish Laboratory, Cambridge, UK). Heemphasized the tremedous progress thathas been made in the last years in DFTcalculations as far as the size of the systems thatcan be treated is concerned. This was especiallyreflected in the posters that were presented at theconference. DFT calculations have become anindispensable tool in the theoretical treatment ofreaction dynamics and growth processes atsurfaces. Still there are many open problems, inparticular in the treatment of electronically excitedstates, as was demonstrated in this conference.In this field the experimentalists are far ahead ofthe theoreticians.

Overall it seems that bringing together expertsfrom different fields at this conference was quite asuccess. The nice atmosphere in the ArabellaBrauneck Hotel in Lenggries which allowed manyrelaxed and informal scientific discussionscertainly contributed to this success. Theexcursion to Munich was also an excellentopportunity to get to know each other, in somecases with unexpected results. Last but not least,the smooth preparation of the conference by theEURESCO staff in Strasbourg, in particularRhona Heywood, was very important for thesuccess of the meeting. Hopefully manyfruitful collaborations will originate from thisconference. Since DFT calculations representsuch a versatile tool to investigate microscopicdetails in the interaction of atoms, molecules andsolids, it is desirable that the EURESCO seriesElectronic Structure will be continued in thefuture, probably visiting other fields like biologicalsystems, coherent control or semiconductortechnology, just to name a few.

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Papers for Publication

• VI Pazzi, P Philipsen, EJ Baerends, GFTantardini: "Oxygen Adsorption on Ag(110):DFT Band Structure Calculations andDynamical Simulations", Surf. Sci. (in press)

• O Krauth, G Fahsold, N Magg and A Pucci:"Anomalous infrared transmission ofadsorbates on ultrathin metal films: Fanoeffect at the percolation threshold", Phys. Rev.Lett. (submitted)

• G Fahsold, A Bartel, O Krauth, N Magg andA Pucci: "IR-optical properties of ultrathin Fefilms on MgO(001) beyond the percolationthreshold", Phys. Rev. B (submitted)

• G Fahsold, A Priebe, N Magg and A Pucci:"An IR-Transmission Spectroscopical Studyof the Influence of Substrate Surface Defectson the Morphology and the ElectronicStructure of Ultrathin Fe Grown onMgO(001)", Thin Solid Films (submitted)

• G Fahsold, G König, A Pucci and K-H Rieder:"Growth of Fe on MgO(001) studied byHelium-atom scattering," Phys. Rev B(submitted)

• VI Pazzi, PHT Philipsen, EJ Baerends and GFTantardini: “Oxygen adsorption on Ag(110):DFT band structure calculations anddynamical simulations,” Surf. Sci. (in press)

• KD Gibson, M Viste, EC Sanchez and SJSibener: "Physical and Chemical Properties ofHigh-Density Atomic Oxygen OverlayersUnder UHV Conditions: (1x1)-O/Rh(111)," J.Chem. Phys. (in press)

• KD Gibson, JI Colonell and SJ Sibener: “TheDecomposition of NO2 on Rh(111): ProductNO Velocity And Angular IntensityDistributions” Surf. Sci. (in press)

• JA Slezak, BD Zion and SJ Sibener:“Enhanced Oxidation Rate of Ni(111) byAtomic Oxygen,” Surf. Sci. Lett. (in press)

• SB Darling, AT Hanbicki, TP Pearl and SJSibener: “Rational Design of InterfacialStructure: Adsorbate-Mediated Templating”,J. Phys. Chem. B (in press)

• TP Pearl and SJ Sibener: “Proximity Heaterfor the Elevated Temperature In Situ VacuumScanning Tunneling Microscopy of MetalSurfaces,“ Rev. Sci. Instrum. (in press)

• AT Hanbicki, SB Darling, DJ Gaspar and SJ.Sibener: “Influence of Steps on the InteractionBetween Adsorbed Hydrogen Atoms and aNickel Surface”, J. Chem. Phys. (in press)

• Wei Li, MJ Stirniman and SJ Sibener: “TheEffect of Cluster Formation on MassSeparation in Binary Molecular Beams,” J.Chem. Phys. (submitted)

• ME Viste, KD Gibson and SJ Sibener:“Heterogeneous Combustion of Benzene onRh(111): Kinetics and Dynamics of CO AndCO2 Production”, J. of Catalysis (submitted -1999).

• J Hahm and SJ Sibener: “Cylinder Alignmentin Annular Structures of MicrophaseSeparated Polystyrene-B-Polymethylmeth-acrylate,” Submitted as a Letter to Langmuir(1999)

• L Diekhöner, A Baurichter, H Mortensen andAC Luntz: “Observations of metastableatomic nitrogen adsorbed on Ru(0001),”J. Chem. Pbys. (submitted)

• M Casagrande, S Lacombe, L Guillemot andVA Esaulov: “Electron transfer processes inthe interaction of fluorine with a chlorinecovered Ag(111) surface,” Surf. Sci. (inpress)

• M Casagrande, S Lacombe, L Guillemot andVA Esaulov: “On ISS and chlorine adsorptionon silver,” Surf. Sci. (in press)

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• L Guillemot, S Lacombe and VA Esaulov“Time dependent characteristics of electrontunnelling processes in H-, O- and F-formation on Ag(111),” NIM B (submitted)

• B Hellsing, J. Carlsson, L Walldén andSÅ Lindgren "Phonon-induced decay of aquantum-well hole: 1 ML Na on Cu(111)",Phys Rev. B (in press)

• L. Lous, L Österlund and B. Hellsing:"Electron Structure and Kinetics of K onGraphite," J. Chem. Phys. (submitted).

• J Carlsson and B Hellsing, "First principlesinvestigation of the quantum well system Naon Cu(111)", Phys. Rev. B (submitted)

• HS. Bengaard, I Alstrup, I Chorkendorff, SUllmann, J.R Rostrup-Nielsen and JKNørskov: “Chemisorption of methane onNi(100) and Ni(111) surfaces withpreadsorbedpotassium”, J. Catal. (accepted)

• T Rasmussen, T Vegge, T Leffers,OB Pedersen and KW Jacobsen: "Simulationof structure and annihilation of screwdislocation dipoles," Phil. Mag. A (accepted)

• J Schiøtz and T Vegge: “Computersimulations of the mechanical properties ofmetals," Science Progress (accepted)

• JH Larsen and I Chorkendorff: “Fromfundamental studies of reactivity on singlecrystals to the design of catalysts,” Surf. Sci.Rep. (accepted)

• J Nerlov, S Sckerl, J Wambach and IChorkendorff: “Methanol synthesis from CO2,CO, and H2 over Cu(100) and Cu(100)modified by Ni and Co”, J. Appl. Cat A(accepted)

• Morgenstern, E Lægsgaard, I Stensgaard, FBesenbacher, M Böhringer, R Berndt, FMauri, A de Vita, R Car and W-D Schneider:“Stability of two-dimensional nanostructures,“J. Appl. Phys. (accepted)

• CE Tripa, TS Zubkov, JT Yates, MMavrikakis and JK Nørskov: “Molecular N2

chemisorption - Specific adsorption on stepdefect sites on Pt surfaces”, (submitted)

• M Mavrikakis, P Stoltze and JK Nørskov:“Making gold less noble”, (submitted)

• RM Watwe, HS Bengaard, JR Rostrup-Nielsen, JA Dumesic and JK Nørskov:“Theoretical studies of stability and reactivityof CHx species on Ni(111)”, (submitted)

• C Bendtsen, OH Nielsen and LB Hansen:“Solving large nonlinear generalizedeigenvalue problems from Density FunctionalTheory calculations in parallel,” (submitted)

• LS Byskov, JK Nørskov, BS Clausen and HTopsøe: “H2 activation on a transition metalsulfide - The role of flexibility”, (submitted)

• S Helveg, JV Lauritsen, E Lægsgaard, IStensgaard, JK Nørskov, BS Clausen, HTopsøe and F Besenbacher: “The atomic-scalestructure of single-layer MoS2 nano-clusters,”(submitted)

• L. Österlund, M Pedersen, I Stensgaard, ELægsgaard and F Besenbacher: “Quantitativedetermination of adsorbate-adsorbateinteractions,” (submitted)

• L Petersen, L Bürgi, H Brune, F.Besenbacherand K Kern: Comment on "Observation oftwo-dimensional Fermi contour of areconstructed Au(111) surface using Fouriertransform scanning tunneling microscopy" byD Fujita, K Amemiya, T Yakabe, H Nejoh, TSato and M Iwatsuki [Surf.Sci 423, 160(1999)], (submitted)

• TR Linderoth, S Horch, L Petersen, S Helveg,M. Schønning, E Lægsgaard, I Stensgaard andF Besenbacher: “Energetics and dynamics ofPt dimers on Pt(110)-(1x2),” (submitted)

• K Højrup Hansen, T Worren, S Stempel, ELægsgaard, M Bäumer, H-J Freund, FBesenbacher and I Stensgaard: “Palladiumnano-crystals on Al2O3: Structure andadhesion energy,” (submitted)

• L Petersen, B Schaefer, E Lægsgaard, IStensgaard and F Besenbacher: “Imaging the

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surface Fermi contour on Cu(110) with STM,”(submitted)

• L Petersen, F Besenbacher and EW Plummer:“Determining the surface Fermi contour:Fourier transform STM,” (submitted)

• TH Rod, A Logadottir and JK Nørskov:“Ammonia synthesis at low temperatures,”(submitted)

• G Papoian, JK Nørskov and R Hoffmann: “Acomparative theoretical study of the hydrogenand ethyl chemisorption on the Pt(111)surface,” (submitted)

• S Dahl, J Sehested, CJH Jacobsen, ETörnqvist and I Chorkendorff: “Surfacescience based microkinetic analysis ofammonia synthesis over ruthenium catalysts”,on the Pt(111) surface," (submitted)

• S Dahl, E Törnqvist and I Chorkendorff:“Dissociative adsorption of N2 on Ru(0001):A surface reaction totally dominated bysteps,” (submitted)

• C Westphal, S Dreiner, M Schuermann, HZacharias: “Holographic reconstruction ofSi(111) atom positions from energy- andangle-resolved photoelectron diffraction,”Surf. Sci. (submitted)

• C Menzel, H Zacharias: “The internal energyof small ammonia clusters in a supersonicbeam and after scattering off LiF(100),”European Physical Journal D, (submitted)

• A.W. Kleyn: “Probing the dynamics ofchemisorption though scattering and stickingin molecular beams,” ed. R. Campargue.Springer Verlag (submitted)

• B Berenbak, B Riedmüller, DA Butler, CTRettner, D.J. Auerbach, S Stolte and AWKleyn.: “Molecular Beam Study on InteractionDynamics in a Reactive System: NO on BareRu(0001),” Phys. Chem. Chem. Phys.(submitted)

• MA Gleeson, J Lourenco, AMC Moutinho, JLos and AW Kleyn: “Ion sputtering as a probe

of liquid surfaces”, Phys. Chem. Com.m(submitted)

• S Wright and E Hasselbrink: “Photochemistryof disilane adsorbed on an H terminatedSi(100) surface,” J. Chem. Phys. (in press)

• H Arnolds, C Rehbein, G Roberts, RJ Levisand DA King “Femtosecond Near-InfraredLaser Desorption of Multilayer Benzene onPt{111}: Spatial Origin of HyperthermalDesorption,” Chem. Phys. Lett. (in press)

• SJ Jenkins and DA King: "PolarisationPromotes Fischer-Tropsch Catalysis,”(submitted)

• A V Walker and DA King: “A MolecularBeam Study of Methane DissociativeAdsorption on Oxygen Precovered Pt{110}(1x2),” Surf. Sci. (in press)

• AV Walker and DA King: “The Reaction ofGaseous Oxygen with Adsorbed Carbon onPt{110} (1x2)”, J. Chem. Phys. (in press)

• WA Brown and DA King: “NOChemisorption and Reactions on MetalSurfaces: a New Perspective”, J. Phys. Chem.(submitted)

• CI Carlisle, DA King, M-L Bocquet, J Cerdand P Sautet: “Imaging the Surface and theInterface Atoms of an Oxide Film on Ag{111}by STM: Experiment and Theory”,(submitted)

• SJ Jenkins and DA King: “Pentaprismane andHypostrophene from First-principles, withPlane Waves”, Chem. Phys. Lett. (submitted)

• Q Ge, SJ Jenkins and DA King: “SurfaceMagnetic Localisation at the Atomic Scale,”(submitted)

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Job Vacancies

POSTDOCTORAL POSITIONS - Technical University of Denmark

Atomic scale simulations of materials, surfaces and biomolecules

Two postdoctoral positions will be available at the Center for Atomic-scale Materials Physics (CAMP) at the

Technical University of Denmark from winter/spring 2000 or later. One position is in the area of atomic scale

simulations of materials processes using molecular dynamics and density functional methods. The other position is

in the area of density functional calculations and modeling of surface chemical and enzymatic processes.

The positions are for two years. The monthly salary is in the range dkr 23.500 - dkr 25.500 (US$ 3600-3900)

depending upon qualifications.

Further questions can be addressed to:

Professor Jens K. Nørskov (norskov@fysik.dtu.dk) or

Professor Karsten W. Jacobsen (kwj@fysik.dtu.dk)

Applications including a CV, publication list and names of three references should be sent as soon as possible to:

Helle Wellejus - e-mail: helle@fysik.dtu.dk

Address: CAMP, Department of Physics, DTU, Building 307, DK-2800 Kongens Lyngby, Denmark

More information about the center can be found at: http://www.fysik.dtu.dk

POSTDOCTORAL POSITIONS - Department of ChemistryUniversity of Cambridge

Postdoctoral positions are available in Dave King’s group, for an experimental surface scientist with uhv experience.

The succesful candidates could work on a novel 4K STM coupled to a pulsed laser system and a molecular beam

doser, or our dual supersonic molecular beam scattering system for studies of catalytic mechanisms, or our

newest instrument, a fibre-optic LEED instrument for low current, low temperature quantitative structural studies.

Interested candidates should contact Dave King at

eld1000@cus.cam.ac.uk;

fax +44(0) 1223 762829;

phone +44 (0) 1223 336338

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POSTDOCTORAL POSTION

University of Erlangen-Nürnberg,

A Postdoc position in surface science is available at the Institute of Physical Chemistry in the group of Prof. Hans-Peter Steinrueck. The research program of the group focuses on the electronic and geometric structure ofbimetallic surfaces and the characterization of their catalytic activity using model reactions. The goal is to obtainvery detailed information by using a variety of experimental techniques that include STM, XPS, ARUPS, IV-LEED,TPD and molecular beam methods. Experience in at least one of these techniques is therefore required. Possibleresearch areas are: (1) Electron spectroscopic studies using synchrotron radiation at BESSY-II in Berlin or at MAX-II in Lund, (2) development of a new photoelectron spectrometer for in-situ studies of surface reactions usingsynchrotron radiation, and (3) investigations of the surface morphology of ultrathin metals layers using variabletemperature scanning tunneling microscopy.

Candidates with a PhD in physics or physical chemistry who are interested in joining an interdisciplinary researchteam should contact:

Prof. Dr. Hans-Peter Steinrück Tel:. (09131) 85-27343, Sekr. (09131) 85-27342

Institut für Physikalische und Theoretische Chemie Fax: (09131) 85-28867

Universität Erlangen-Nürnberg Email: steinrueck@pctc.chemie.uni-erlangen.de

Egerlandstrasse 3, D-91058 Erlangen, Germany http://www.chemie.uni-erlangen.de/pc2

2 - POSTDOCTORAL POSITIONS

TMR Network in “Surface Photochemistry”University of Essen and University of Liverpool

Candidates are invited to apply for post-doctoral positions to work in the EU funded TMR network "Surface

Photochemistry". Applicants, who will be below 35 years old, should have a PhD in Chemistry or Physics and

should be from an EU member state other than Germany (for Essen) or Britain (for Liverpool). The positions are

available at the University Essen and the University of Liverpool and the contracts are negotiable from 1 to 3 years.

Further information may be obtained from

http://www.phchem.uni-essen.de/TMR/

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PH.D and POSTDOC POSITIONS – University of Leiden

A number of positions are available. For further information contact

Dr Mischa Bonn – m.bonn@chem.leidenuniv.nlProfessor Dr Aart Kleyn – A.Kleyn@chem.leidenuniv.nl

Dr Ben Niewenhuys – knegtel@chem.leidenuniv.nl

Leiden Institute of Chemistry - Gorlaeus Labs/Leiden University, PO Box 9502 - 2300 RA Leiden- NL

Femtosecond surface reaction dynamics

1 PhD or post-doc position for the work on ultrafast reaction dynamics with femtosecond lasers. The succesfulapplicant will employ femtosecond infrared surface spectroscopy to gain important insights into elementaryprocesses at simple liquid surfaces. Collaborations include a.o. dr. Huib Bakker (Amsterdam), and theoreticalsupport from dr. G.J. Kroes (Leiden). - For information, contact: dr. Mischa Bonn.

1 PhD or post-doc position for work on ultrafast reaction dynamics with femtosecond lasers in UHV. This projectinvolves the study of the timescales of elementary reaction steps of simple reactants on metal surfaces. Thisproject is a joint effort with dr. Martin Wolf (Berlin).- For information, contact: dr. Mischa Bonn.

Surface photochemistry

2 PhD or post-doc positions for work on surface photochemistry. The aim of this project is to shed more light onthe photochemical reactions that take place at metal and ice surfaces using experimental methods from thefields of basic surface science, physical chemistry and molecular physics. There are several projects running onthese topics using two surface science apparatus that share a large collection of lasers with nanosecond untilfemtosecond pulse duration. - For information, contact: prof. dr. Aart W. Kleyn.

Molecular beams

1 PhD or post-doc position for work on molecular beams. The research will involve molecular beam scatteringwith state specific detection of product molecules, and femtosecond pump-probe spectroscopy. Contact: prof.dr. Aart W. Kleyn.

Catalysis

1 PhD or post-doc position is available for research of noble metal-transition metal oxide surfaces (STW), incollaboration with prof. dr. A. Bliek (Amsterdam) and prof. dr. J.W.M. Frenken (Leiden). Contact: dr. Ben E.Nieuwenhuys.

1 PhD or post-doc position is available for research in the field of oscillatory behavior of surfaces of surfacereactions (NRSC-Catalysis), in collaboration with prof. dr. R.A. van Santen (Eindhoven). For information,contact: dr. Ben E. Nieuwenhuys

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Meeting Announcements

19th International Conference on Atomic Collisions in SolidsICACS-19

Paris, France - 29 July - 3 August 2001

ICACS is a biannual meeting, which deals with physical and chemical phenomena induced by the interactionof low and high energy beams of charged or neutral particles with matter: surface and bulk of solids, liquidsand biomaterials. The most recent meetings have been held in Odense (Denmark, 1999) and Beijing (China,1997).

The objectives of the Paris ICACS-19 are to assess the state of the art in the current understanding of avariety of phenomena such as energy losses of ions, radiation damage, sputtering, excitation, ionisation andelectron emission as well as collision induced reactions and desorption of charged or neutral atomic andmolecular species. Fundamental aspects of electron transfer in particle surface/bulk interactions will behighlighted. While the programme will focus mainly on the interaction of atomic, molecular and clusterprojectiles, related processes induced by electron, positron and photon beams, will also be considered.Pertinent materials are pristine or adsorbate covered metals, semiconductors, insulators, as well as polymers,bio-materials and liquids. Macro to nano structures of these materials will be considered. New developmentsin experimental techniques may be presented.

The emphasis of the meeting is on fundamental processes, but challenging scientific and technologicalapplications in physics, chemistry, biology and medicine will be considered. The programme will consist of oraland poster presentations and sufficient time for informal discussions will be allocated.

Contact : Vladimir A.Esaulov,

Laboratoire des Collisions Atomiques et Moleculaires

bat.351, Universite de Paris Sud

91405 Orsay Cedex

France

phone : (33)1 69 15 76 80 - fax : (33) 169 15 76 71e-mail: icacs19@veof1.lcam.u-psud.fr

http://veof1.lcam.u-psud.fr/idc/icacs19.html

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JVC-8 8th JOINT VACUUM CONFERENCEof Croatia, Austria, Hungary and Slovenia

4-9 June 2000 - Pula, Croatia

Organized by the Croatian Vacuum Society with the sponsorship of IUVSTA and Ministry ofScience and Technology of Croatia

Scope of the conference:Reporting results of original scientific work in the fields of

• Applied Surface Science, • Surface Science,• Electronic Materials • Thin Film• Nanometer Structures, • Vacuum Metallurgy,• Plasma Science and Technique, • Vacuum Science

This will be achieved through plenary and invited lectures, oral and poster contributions.

International Organizing Committee:Milorad Milun (conference chairman), - Gyorgy Radnoczi, Hungary, - Herwig Bangert, Austria,- Milko Jaksic,

Croatia, - Sandor Bohatka, Hungary, - Ognjen Milat, Croatia, - Manfred Leisch, Austria - Andrej Pregelj, Slovenia –Nikola Radic, Croatia, - Vinko Nemanic, Slovenia

International Programme Committee:Nikola Radic (chairman), - Milorad Milun, Croatia, - Rudolf Dobrozemsky, Austria, - Petar Pervan, Croatia, -

Monika Jenko, Slovenia, - Branko Pivac, Croatia, - Tivadar Lohner, Hungary, - Herbert Stoeri, Austria, -Vladimir Matolin, Bohemia, - Tamas Szoereny, Hungary, - Marian Vesely, Slovakia, - Anton Zalar, Slovenia

List of plenary lecturers:• Alessandro Borghesi, Universita degli Studi di Milano-Bicocca, Italy• Peter D. Johnson, Brookhaven National Laboratory, USA• Yves Pauleau, L'Institut National Polytechnique de Grenoble, France• Boris Sinkovic, Physics Department, University of Connecticut, USA• Klaus Wandelt, Institute of Physical and Theoretical Chemistry, University Bonn, Germany

There will be also 14 invited speakers whose names will be announced soon.

Conference language: - EnglishConference venue:The conference will take place in a modern hotel Histria located 5 km from the Pula downtown on a smallpeninsula Punta Verudela (buses commute every 15 minutes). Beaches surround the hotel on its three sides.Two swimming pools are located right in the hotel. Numerous tennis courts, yacht clubs and other sportingfacilities offer a wide palette of opportunities to have a great time during the conference free time. For thosewho would like to see more of this beautiful piece of land a number of excursions will be organized daily tovarious popular sites. Pula is an old town with many historical sites and an ancient history.

Pula may be reached by car, bus, train, airplane and ship.

Important dates:Abstract deadline: 1st March 2000Advanced registration: 1st May 2000

FURTHER INFORMATION http://faust.irb.hr/~jvc8/ contains all relevant informationregarding the Conference, Contact address details –See DIARY PAGE

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Diary Page

6th March 2000Astrophysical Chemistry Group/Royal Astonomical Society, Young Researchers Meeting,London. A one-day meeting aimed primarily at PhD students and Postdocs. Further information at- http://www.nottingham.ac.uk/~pczhjf/astrochem.htm orHelen Fraser - pczhjf@unix.ccc.nottingham.ac.uk

April 3rd – 8th 2000The Second San Luis Symposium on Surfaces, Interfaces and Catalysis, Mar del Plata(Conference and Summer School). Scholarships available for students from USA. Contacts: N.America: W Tysoe at wtt@uwm.edu, Latin America G. Zgrablich at giorgio@unsl.edu.ar,Europe: R Lambert - rml1@cam.ac.uk. or surface.chem.uwm.edu/conference.html

30th May 2000- 3rd June 20008th International Conference on Theoretical Aspects of Heterogeneous Catalysis - CAT 2000,La Colle sur Loup, Alpes-Maritimes, France 30/05/2000 - 03/06/2000. further information from:cat2000@catalyse.univ-lyon1.fr

JVC – 8th Joint Vacuum Conference or Croatia, Austria, Hungary and Slovenia, at Pula,Croatia. Organised by the Croatian Vacuum Society with the sponsoship of IUVSTA and Ministryof Science and Technology of Croatia. Conference Chair: M Milun, Institute of Physics, Zabgreb.Further information at - milun@ifs.hr or http://faust.irb.hr/~jvc8/ or fax: (+385)–1-4680399

10-14 July, 2000Internatinoal Converence on Solid Films and Surfaces (ICSFS-10), Princeton University, USA.Preliminary information now avaiable on the web: http://www.pmi.princeton.edu/ICSFL/Email: icsfs-10@ee.princeton.edu

4-6th September 2000Faraday Discussion 117 – Electron Excited States at Surfaces University of Nottingham, UK.Chairman: Professor S Holloway, (University of Liverpool, UK.) Further Informationhttp://www.rsc.org/lap/confs/faradischome.htm

11th-15th September 2000Adriatico Research Conference on Lasers in Surface Science, Trieste, Italy. Organisers H-JFreund, TF Heinz and H Zacharias.Further information available from: hzach@pop.uni-muenster.de

1st-5th October 2001Ecasia ’01 9th European Conference on application so Surface and Interface Analysis.Maresilles France. Further Information is at ecasia01@enscp.jussieu.fr orhttp://www.enscp.jussieu.fr/ECASIA/

SUMMER 2001Surface Science Summer School. Following the School in Dronten, Netherlands this summer,the next in the series will be held in READING, UK. Chair of Organising Committee: MikeBowker. Further details to follow.

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