A Kinetic Model of the Accommodation Pumping Phenomenon

Abstract

A simple kinetic model of the accommodation pumping phenomenon is developed. This model is consistent with the earlier suggestion that the extent to which specular reflection occurs from smooth Pyrex surfaces is dependent upon the velocity of the atoms. It is shown that the upper limit for the pump ratio (PA/PB) is 2, but that in any real situation this ratio would be less than this value. The model is used to show that the deviation of the thermal transpiration ratio from the ideal value, (T1/T2)1/2, should be the same as the accommodation pumping ratio for the same tubing with the same temperature difference.