Simple Model for the Energy Accommodation Coefficient

Abstract

Quantum mechanical expressions for the energy accommodation of a gas at a solid surface are developed using the general theory of inelastic surface scattering as developed by Manson and Celli. Calculations are presented for the accommodation of helium at a simplified model of a tungsten surface. The phonon spectrum at the surface is taken to be that of a semi-infinite isotropic continuum, and contributions to the accommodation are obtained from bulk, mixed, and Rayleigh phonon modes. For temperatures not too small the calculations agree qualitatively with experiment, and exhibit the property that the accommodation is nearly independent of surface temperature over a large range.