OXYGEN-ADSORPTION ON CESIUM-GRAPHITE INTERCALATION COMPOUNDS - PHOTOEMISSION-STUDIES OF THE DAMAGES CAUSED BY X-RAY-IRRADIATION AT 100 K

Oxidation at 100 K of the surfaces of Cs-graphite intercalation compou nds (Cs-GICs) leads to the formation of one oxide (O2-), two peroxide (O-2(2-)) and one superoxide (O-2(-)) species. The oxidised Cs-GIC lay er is modified under X-ray irradiation and this modification was there fore investigated with W and X-ray photoelectron spectroscopies. X-ray irradiation dissociated the dioxygen species and formed the O- and O2 - species. Only one peroxide species was not fully decomposed after lo ng time irradiation. Before X-ray irradiation, the oxidised layer was constituted by islands which did not totally cover the surface, wherea s after X-ray irradiation, this layer was spread over the whole surfac e. X-ray irradiation therefore transforms all the oxygen species via s econdary electrons and modifies the structure of the oxidised layer.