Th. Kammler et al., A KINETIC-STUDY OF THE INTERACTION OF GASEOUS H(D) ATOMS WITH D(H) ADSORBED ON NI(100) SURFACES, The Journal of chemical physics, 106(17), 1997, pp. 7362-7371
The kinetics of reactions which occur upon subjecting D(H) covered Ni(
100) surfaces with H(D) atom fluxes were investigated. At 120 K surfac
e temperature in the H-->D-ad reaction HD and D-2 were observed as rea
ction products, in the D-->H-ad reaction HD and H-2 were reaction prod
ucts. As the reaction temperature was well below the hydrogen desorpti
on temperature, a direct reaction step, like in the Eley-Rideal (ER) m
echanism, is suggested to operate for HD production. However, the char
acteristics of the HD formation kinetics observed in the present study
contradict an essential element of the ER: mechanism the rate: of HD
formation is not proportional to the surface coverage of the adsorbed
reaction species D or H under impact of a flux of H or D atoms. Theref
ore, a modification of the mechanistic description of atom/surface rea
ctions seems necessary. This modification should allow for reaction pr
oducts which are completely unaccounted for in the ER picture: D-2 fro
m H-->D-ad and H-2 from D-->H-ad reactions. The observed strong isotop
e effects in the reaction efficiencies support mechanisms in which the
impinging gas phase atoms get trapped in the surface potential well p
rior to reaction. (C) 1997 American Institute of Physics.