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 compounds (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 layer is modified under X-ray irradiation and this modification was therefore 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 long time irradiation. Before X-ray irradiation, the oxidised layer was constituted by islands which did not totally cover the surface, whereas after X-ray irradiation, this layer was spread over the whole surface. X-ray irradiation therefore transforms all the oxygen species via secondary electrons and modifies the structure of the oxidised layer.