The chemisorption of several diatomic gases onto a W(210) plane and a polycrystalline tungsten surface

Abstract

Plots of the sticking probabilities of CO and H 2 on the (210) face of tungsten against the fraction of the surface covered were found to be sigmoid. This shape has already been observed for at least one other system (15). It is explained by suggesting that adsorption on neighboring positions linearly increased the chemisorption activation energy experienced by a molecule in the mobile precursor state. The desorption spectra of CO on the W (210) plane contained an α and a β peak and an analysis of the spectra produced by CO on polycrystalline tungsten demonstrated that the β 3 peak desorbed by a second order reaction. The change in the work function when CO adsorbed on the W(210) face showed that the surface filled in two stages. The surface moment was constant during each stage. Hydrogen initially increased the work function of the W(210) plane. When the fraction of the surface covered reached 0.75, the work function was at a maximum and then decreased somewhat.