Chemisorption of Nitrogen on Tungsten

Abstract

The amount of nitrogen chemisorbed on a polycrystalline tungsten ribbon has been measured as a function of the temperature of the ribbon and the pressure in the region of less than one monolayer. By assuming the condensation coefficient to be insensitive to the temperature of the gas, values of the thermodynamic functions are determined. It is found that N₂ is adsorbed on tungsten as atoms with a heat of adsorption of 5.0 ev per molecule (±10%) independent of coverage over the experimental range of coverage. In the temperature range 1150–1670°K the differential entropy of adsorption is of the order expected for adsorption on localized sites, with a moderate contribution from the vibrational degrees of freedom.