An overview on the electronic and vibrational properties of adsorbed CO

Abstract

This paper addresses itself to the question of the inadequacy of the donation-backdonation model for treating CO adsorption (both strong and weak) especially in the lihght of recent measurements by ARUPS, I-UPS, HREELS and NEXAFS to identify the 2 pie level with or without occupancy The variation, including the sign (decrease or increase) of the work functson as a result of CO adsorption, is ldenufied to be due to the reversal or change in magnitude of polarity of the molecule in the adsorbed state. The reversal of the ordenng of the valence states according to thus model becomes a natural consequence of the relaxation of the equlibrium internuclear d-stance. The systematlcs in the adsorption super-structures and the variation of other adsorption parameters especially that of adsorption energy are considered for both group VIII and I b metals. The characteristics of the vibrational properties of adsorbed CO on group VIII and Ib metals are considered in terms of the electronic properties with a vtew to obtain possible correlations in the future. The need for more accurate measurements to evaluate the 5sigma-1pie separation in the adsorbed state is indicated, which will enable. It is hoped a synthesls to be made of a unified correlation between internuclear distance, wave number of (C-O) and delta(5sigma-lpie) within a single framework model The charactensitcs of nitrogen 0soelectronsc with CO) adsorption on group VIII metals are also considered for comparison