Some observations on the surface sensitivity of photoelectron spectroscopy

Abstract

As an essential preliminary to applying a number of different photoelectron spectroscopic methods to investigate the mechanism of solid/gas reactions their surface sensitivity has been explored. Data are reported for the sensitivity of e. s. c. a. for H₂O, CO₂ and CO adsorbed on Au. Also the interaction of mercury vapour with Au has been studied, adsorption and lattice penetration of the mercury being observed by monitoring the Hg(4f) peaks. In general, less than 10% of a monolayer of H₂O and CO₂ is detectable by X-ray photoelectron spectroscopy. Significant chemical shifts are observed between C(1s) present as an impurity in the Au lattice and C(1s) in adsorbed CO₂, and also between O(1s) in H₂O(ads) and CO₂(ads). The surface sensitiveness of u. v. and X-ray photoelectron spectroscopy are compared.