We examine the recombination and desorption of hydrogen from an aluminum(111) surface focusing on desorption processes that lead to the formation of dihydrogen and aluminum hydride (presumably alane). In addition to simple temperature-programmed reaction spectroscopy (TPRS), we examine the perturbations which occur to the desorption kinetics of these species as a result of the energy transfer due to collisions of a xenon beam at 1.6, 2.8, and 3.6 eV with a hydrogen covered surface. Whereas the recombinative desorption of dihydrogen from an Al(111) surface nominally follows an unusual zero-order rate law, bombardment of a hydrogen-covered surface with an energetic xenon atom leads to a kinetic profile more closely modeled by a higher reaction order. It also was found that upon exposure to the beam, the peak area (and thus the desorption yield) for the H2 desorption was reduced 5-25% depending on the length of exposure whereas for the aluminum hydride the percent reduction ranged from 10-80%. This suggests that both a stimulated etching and a change in state result from the beam exposure. We present evidence that suggests that the initial state of the bound hydrogen may involve at least in part a subsurface occupation.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry