The adsorption of hydrogen on tungsten

Abstract

When a gas atom or molecule strikes a solid surface it may either rebound, the collision being accompanied by an interchange of energy, or it may be adsorbed. In order to obtain a satisfactory interpretation of either type of phenomenon it is necessary to know the nature of the atoms concerned. This is comparatively easy for the gas, but the solid requires closer attention. The essential condition is that the surface of the solid is completely freed from adsorbed films of impurity before the experiment starts and remains free. In the earlier papers in which an account of the development of the present work on this problem has been given, it has been shown that the average interchange of energy when gas atoms strife and rebound from a slightly hotter metal surface is very markedly affected by the presence of such adsorbed films. The accommodation coefficient is a quantitative measure of the efficiency of this interchange and for neon with a tungsten surface the removal of all adsorbed films caused the accommodation coefficient to change almost by an order of magnitude (0.6 for an ordinary surface covered with adsorbed films of impurity and about 0.07 or 0.08 for a bare tungsten surface). This suggested that the accommodation coefficient of neon could be used as an indicator in studying the adsorption on bare tungsten of known gases mixed with the neon. The application to the study of the adsorption of hydrogen of the method that has been developed with this idea as a basis is described in 2.