Infra-red spectra and spectral shifts of CO adsorbed on evaporated alkali-halides. Part 2.—Films of caesium salts

Abstract

Infra-red spectra of CO adsorbed on CsCl, CsBr and CsI films were recorded at 77 K, at different surface coverages. The absorption bands appeared as doublets, one component of which was shifted towards lower frequency and the other towards higher frequency with respect to the gas phase. For CsCl as adsorbent, the energy of adsorption was calculated for various sites and orientations, and for various equilibrium planes exposed to the adsorbate. In three cases, good agreement was found with experimental isosteric heat of adsorption. Spectral shifts were calculated using the perturbation method, the adsorption energy serving as the perturbing potential. Two models were assumed for the behaviour of the adsorbate. Fairly good agreement with the experimental values of Δν was found.