A model for gas-surface distribution functions

A technique to incorporate the results of complete gas-surface trajectory computations into rational mathematical expressions for the exiting gas distribution functions is outlined. These expressions are of the generalized Gaussian, or ellipsoidal, type. Specific examples show how the undetermined parameters of such models are determined from various higher moments that are accessible only through complete sets of trajectory computations. The resulting distribution function models give reasonable representations of the flux distributions computed from the trajectory calculations, and also those measured in corresponding laboratory experiments.