Resonant electron and ion emission and desorption mechanism in rare earth oxides

Resonant electron and ion emission and desorption mechanism in rare earth oxides

A687 213 Surface Science 163 (1985) 273-284 North-Holland, Amsterdam WATER PRODUCTION ATMOSPHERES L.-G. PETERSSON, Department S-581 H.M. DANNETUN ...

112KB Sizes 0 Downloads 10 Views

A687 213

Surface Science 163 (1985) 273-284 North-Holland, Amsterdam

WATER PRODUCTION ATMOSPHERES L.-G. PETERSSON, Department S-581

H.M. DANNETUN

of Physics and Measurement

83 Linkiipmg,

Received

ON PALLADIUM and

IN HYDROGEN-OXYGEN I. LUNDSTROM

Technology’, Llnkiiping

Unioersrty.

Sweden

20 February

1985

We have studied the water production on combination with work function measurements, tive measurements on a Pd-SiO,-Si structure. pressure ratio is confirmed. Above the critical increasing oxygen pressure and increases with ratio, the water production rate is proportional hydrogen pressure. These features, together with are described by a simple Langmuir-Hinshelwood lateral mobility and that both hydrogen and adsorbed oxygen.

Pd in various oxygen-hydrogen atmospheres in photoelectron spectroscopy and hydrogen sensiThe existence of a critical oxygen to hydrogen ratio. the water production rate decreases with increasing hydrogen pressure. Below the critical to the oxygen pressure and independent of the the variations in oxygen and hydrogen coverage, model, assuming that hydrogen has a large oxygen adsorption-dissociation is blocked by

285

Surface Science 163 (1985) 285-302 North-Holland, Amsterdam

QUANTUM CHEMICAL STUDIES OF THE CHEMISORPTION OF ATOMIC HYDROGEN ON COPPER AND SILVER CLUSTERS * J. FLAD, G. IGEL-MANN, M. DOLG, H. PREUSS and H. STOLL Insritut ftir Theoretische Fed.

Chemie,

Unioersitiit Stuttgart,

Pfaff enwaldrmg

55, D 7000 Srutrgart

80,

Rep. of Germany

Received

18 March

1985; accepted

for publication

11 July 1985

The adsorption of atomic hydrogen on group lb elements has been studied, by means of pseudopotential calculations, for copper and silver clusters with up to six atoms, Various adsorption positions and spin multiplicities have been considered, and corresponding equilibrium internuclear distances, binding energies and force constants have been calculated.

Surface Science 163 (1985) 303-314 North-Holland, Amsterdam

303

RESONANT ELECTRON AND ION EMISSION AND MECHANISM IN RARE EARTH OXIDES J. SCHMIDT-MAY, F. SENF, J. VOSS and C. KUNZ II. Insfitut ftir Experimentalphysik, Fed. Rep.

Uniuersitiit Hamburg,

of Germany

A. FLODSTRijM Maxlab,

University of Lund,

S - 22007

Lund, Sweden

D -2000

Hamburg

DESORPTION

SO,

A688 R. NYHOLM

The resonant enhancement in photoelectron spectra at the 4d edges of rare earth atoms and metals is also found in yield spectra of desorbed ions from the surfaces of the oxides of Sm. Eu and Yb following the photon excttation. The analysis of the 4d --t 4f resonance leads lo a picture of an Indirect mechanism of ion desorption which is mamly caused by the flux of energetic 4f photoelectrons from the bulk. In this case the dominant desorption through secondary processes hmits the use of the photon-stimulated desorption (PSD) to determine 1n which type of atom the desorbing species was attached.

Surface Science 163 (1985) 315-334 North-Holland. Amsterdam

ION BEAM CRYSTALLOGRAPHY IV. Si(lll)-(2 X 1)

OF SILICON SURFACES

L. SMIT

IBM

Th,jmas

J. Watson

Research Center, P. 0. BOX 718, Yorkton~n Herghts.

.l’ew York lo.i%

CSA

and J.F. VAN

DER VEEN

FOM Insrrrutefor Atomic and Molecular Phystcs, P.O. BOX 4lKX.j. 1009 DB Amsterdam, The Netherlands Received

11 May 1985; accepted

for publication

10 July 1985

The atomic geometry of the (2 x 1) reconstructed Si(l11) surface has been determlned with ion shadowing and blocking. The reconstruction involves large displacements parallel to the surface. Comparison of the experimental results with computer simulations for various reconstructton models excludes the buckling and the n-bonded molecule models, and shows consistency with the n-bonded chain model only. A structure search around the r-bonded chain model shows an optimal fit between experiment and simulations when the model includes a tilt of the upper and lower chains with respect to the surface plane. A detailed account of experimental and computational techniques is giver