THE INTERNAL AND TRANSLATIONAL ENERGY-DEPENDENCE OF MOLECULAR CONDENSATION COEFFICIENTS - SF6 AND CCL4

In this paper we describe a series of beam-surface scattering experime nts which examine the internal and translational energy dependence of the molecular condensation probabilities for CCl4 or SF6 colliding wit h their respective condensed phases. It has been conclusively shown th at thermal excitation of a polyatomic molecule's rotational and vibrat ional degrees of freedom can inhibit its probability of sticking upon impact with a cryogenically cooled surface. This effect is most pronou nced in the limit of low incident kinetic energy, and essentially vani shes at higher velocities. As part of these experiments; we have also obtained the angular and velocity distributions for reflected SF6 and Kr which have been used to examine the energy and momentum exchange of these gases with their respective condensed phases. Our findings sugg est that heterogeneous laser isotope separation schemes based on preco llision molecular excitation may warrant further investigation.