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.
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