Recombination reactions on Ni(111)

A206 549

Surface Science 141 (1984) 549-566 North-Holland, Amsterdam

SURFACE STRUCTURE SCATTERING

ANALYSIS

USING LOW ENERGY ION

I. Clean Fe(OO1) L. MARCHUT, AT&T

T.M. BUCK, G.H. WHEATLEY

Bell Laboratories,

Received

9 August

and C.J. McMAHON,

Jr. *

Murray Hill, New Jersey 07974, USA

1983; accepted

for publication

28 February

1984

A clean Fe (001) unreconstructed surface has been analyzed using Low Energy Ion Scattering with time of flight energy analysis. The intensity of scattered 9.5 KeV Ne+ ions and neutrals was measured as a function of elevation and azimuth of the incoming beam while keeping a fixed scattering angle of 90 O. The observed intensity variations can be described by considering the shadowing and blocking of the second and third atomic layers. A simple Firsov potential was used to calculate the shadow cone dimensions. The good agreement between the observed and calculated variations in scattered intensity demonstrates the utility of this relatively simple technique for preliminary analysis of surface structure.

Surface Science 141 (1984) 567-579 North-Holland, Amsterdam

RECOMBINATION

Jay B. BENZIGER

567

REACTIONS

* and Richard

Deparrmenr of Chemical Engmeerrng, Received

9 August

1983; accepted

ON Ni( 111)

E. PRESTON

Princeton

University, Pnnceron,

for publication

23 February

New Jersey 08544, USA

1984

The dissociative adsorption and recombination of CO, N,, SO, and 0, on Ni(ll1) has been studied by LEED, AES and TPD. The kinetic parameters were determined for 0 + 0, N + N, All four reactions displayed second order kinetics with pre-exS + 0, Ccarb,ds + 0 recombination. ponential factors of lo-**’ cm2/atom. s. The activation energies were E, + ,, = 440 kJ/mol, E N+N = 210 kJ/mol, The kinetics of the Es+O = 310 kJ/mol and ECcsrb,d.+O= 175 kJ/mol. C sraphlts +0 recombination were found to be first order indicating a condensed graphite phase with reaction at the phase boundary. These kinetics were further complicated due to an apparent phase transition of the adsorbed graphite at 970 K. The TPD results were used to estimate heats of adsorption. These estimates correlated with the heats of formation of bulk compounds.

Surface Science 141 (19X4)580-590 North-Holland. Amsterdam

580

AB INITIO MO STUDY SURFACE Hisayoshi KOBAYASHI, Masaru YAMAGUCHI

OF ACETYLENE Hiroyuki

Faculty of Lturng Science, Kyoto Prefectural Received

5 September

1983; accepted

ADSORBED

TERAMAE

*, Tokio

ON Ni( 111) YAMABE

** and

Umuersrty, Kvoro. Japan

for publication

7 March

1984

and 125’, respectively. These values agree well with the corresponding values determined by UPS, ELS and LEED intensity analysis studies. The interaction between acetylene and the cluster in the chemisorption system is analyzed in terms of the orbital mixing, and the modes of charge transfer are concisely represented with the aid of the Interaction Frontier Orbitals.