Time and space dependent energy distributions of atoms from surfaces

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Abstract
Time and space dependent energy distributions for atoms effluxing from a surface are obtained analytically using the harmonic soft‐cube model. The effluxing atoms consist of a desorbed fraction and a reflected fraction. The tangential energy distribution of the desorbed fraction is assumed to have equilibrated with the surface, while that of the reflected fraction is assumed unchanged. The normal energy distribution of the desorbed fraction depends on the adsorbed atom energy distribution obtained here from the governing master equation without the steady state approximation. The normal energy distribution of the reflected fraction is obtained from the soft‐cube model for the collision dynamics. As expected, due to the gas–surface potential well, the desorbed fraction of the flux from the surface has a noncosine distribution. The reflected fraction has a lobular distribution about the specular angle. Time dependent scattering patterns are obtained as a function of the interacting atomic species, the incident energy distribution, and the gas and surface temperatures. Comparison with experimental desorption and adsorption rates and with scattering patterns from clean surfaces is possible.