Dynamics and kinetics of subsurface absorption and desorption for the system hydrogen (deuterium)–Ni(111)

Abstract

We have investigated the desorption kinetics of subsurface hydrogen (deuterium) from Ni(111) with angle resolved thermal desorption spectroscopy. For the first time we directly compare the desorption from subsurface states populated either by dosing with hydrogen atoms or by implantation of molecular hydrogen ions. For the various dosing modes subsurface desorption proceeds at clearly different temperatures. The angular distribution of the desorption probability for all subsurface states can be described by a cos n Θ function with n<1, whereas desorption from the surface states is strongly forward focused ( n=4.5). The initial sticking coefficient of H (D) on the clean Ni(111) surface is 1.0 and independent of the angle of incidence. The “initial absorption” coefficient for atomic hydrogen at the H-saturated surface is about 0.1. Interaction of atomic hydrogen with the H-saturated surface takes place in form of abstraction, adsorption and absorption simultaneously.