The exchange of energy between gas atoms and solid . II.—The temperature variation of the accommodation coefficient of helium

In an earlier paper it has been shown that, by paying careful attention to the removal of films of adsorbed gas, considerably lower values are found for the accommodation coefficient of helium with a tungsten surface than those ordinarily measured. These results for a clean surface, as opposed to those given by a surface covered with adsorbed films of unknown, constitution and arrangement, must form one part of any theory of the interaction between gas atoms and a solid surface. The discovery by Stern of the phenomena of atomic reflection and diffraction shows that this theory must be treated from the point of view of wave mechanics. In the present paper data are given for the variation of the accommodation coefficient of helium with a tungsten surface between ordinary temperatures and —194°C. The apparatus used was similar to that used in the earlier experiments, but in order that the glass-metal seals should stand immersion in a bath of liquid nitrogen the experimental tube was made of Pyrex glass. The value obtained at room temperature with the earlier apparatus was confirmed with the new one.