Rate constants for thermal desorption of physisorbed argon and neon from a xenon(111) crystal face have been calculated using a generalization of Slaterrsquo;s unimolecular reaction rate theory, with a particular emphasis being placed on an investigation of the dependence of these rates upon the degree of surface coverage and upon the lattice motion of the solid. For argon our Monte Carlo results show a nonhyphen;negligible coupling between adatom dynamics and the thermal vibration of the crystal surface which leads roughly to a 20percnt; enhancement of the desorption rate. The increase is, however, only half as great for neon, with a statichyphen;solid description becoming appropriate as the system temperature is decreased. The adatom concentration effect on the kinetics also appears to be more dramatic for adsorbed argon than for neon, presumably as a consequence of the longer range and greater strength of the argonndash;argon potential.
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