Some Applications of Molecular Beam Velocity Spectroscopy to Evaporation and Energy Exchange.

摘要

Velocity distributions have been determined for molecules evaporating into vacuum from surfaces of polycrystalline hexachlorobenzene and sulfur. Analysis of the distributions indicates that they are Maxwellian and correspond to the surface temperature. In the case of sulfur,it appears that more than one molecular species is involved. It seems likely that the composition of the evaporative flux corresponds to vapor in equilibrium with the solid. Beams from free jets of carbon dioxide as well as methane and its chlorinated derivatives have also been analyzed. Substantial amounts of internal energy survive the expansion and are retained in the beam molecules. Under some conditions it is possible to extract absolute relaxation rates from the velocity spectra. In the case of methane,for example, a value of 15was obtained for the characteristic rotation-translation collision number. This value is in good agreement with ultrasonic dispersion measurements. (Author)