ECR study of electron photoemission from gas solids

Abstract

Electron photoemission from rare gas solids (RGS) was obtained using VUV open discharge sources. Temperature dependencies of the photoyield were measured by recording the ECR absorption of free electrons emitted from the RGS surfaces. Two types of photoemission were observed for solid Ne: intrinsic and extrinsic. The first one was attributed to the escape of the electrons photoexcited into the conduction band (CB), while the second one was an exciton assisted emission. In both cases, the electron yield is governed by the surface processes. In heavier rare gases, Ar and Kr, the intrinsic photoemission was found to be sensitive to the trapping of CB-electrons in the bulk. For the solid Ne, doping experiments (He, CH4, D2, CO, O2) revealed that dopant molecules and atoms which have negative or small positive affinities suppress the photoyield by “deteriorating” surface sites active for the electron emission, while impurities with large positive affinities quench the photoemission by scavenging CB electrons in the bulk as well as on the flat surface. Evidence is presented of the transient mobility of CH4 molecules adsorbed on the solid Ne at liquid helium temperatures.