Molecular beam study of the H/sub 2/--D/sub 2/ exchange reaction on stepped platinum crystal surfaces: Dependence on reactant angle of incidence

Journal Article · Thu Dec 01 04:00:00 EST 1977 · J. Chem. Phys.; (United States)

OSTI ID:5367927

Salmeron, M; Gale, R J; Somorjai, G A

The exchange reaction H/sub 2/+D/sub 2/..-->..2HD was studied as a function of the angle of incidence (polar and azimuthal) of the beam of reactants on two stepped platinum surfaces, the Pt(S) -(6(111) x (111)) and Pt(S) -(5(111) x (111)). The reaction probability was found to depend markedly on the direction of approach of the reactants to the step structure. The production of HD is highest when the reactants strike the open side of the step structure, decreasing by approximately a factor of 2 when the inner corner of the step is shadowed. These variations are intimately related to the geometry of the stepped surfaces and cannot be attributed to an activation energy barrier for adsorption. The observed dependence can be accounted for in a simple model, assigning different activities for H--H bond breaking to the step and terrace sites. For the best fit with the experimental data we find that the activity of a step site is seven times that of a terrace site at normal incidence.

• Research Organization: Materials and Molecular Research Division, Lawrence Berkeley Laboratory, and Department of Chemistry, University of California, Berkeley, California 94720
• OSTI ID: 5367927
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 67:11; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BEAMS
CHEMICAL REACTIONS
CRYOGENIC FLUIDS
DEUTERIUM
ELEMENTS
FLUIDS
HYDROGEN
HYDROGEN ISOTOPES
ISOTOPES
ISOTOPIC EXCHANGE
LIGHT NUCLEI
METALS
MOLECULAR BEAMS
NONMETALS
NUCLEI
ODD-ODD NUCLEI
PLATINUM
PLATINUM METALS
STABLE ISOTOPES
SURFACES
TRANSITION ELEMENTS