Desorption of physisorbed and condensed gases on cold surfaces by electron irradiation

Abstract

The electron stimulated desorption of H2 physisorbed on porous layers of Xe was investigated. The species of ions desorbed were revealed by means of the time-of-flight technique. The neutral desorbed was also detected by the measurement of the partial pressure rise during electron irradiation. The absolute desorption yields of the ions (H+, H3+, and Xen+) and the neutral (H2) are presented. The desorption yields were found to depend on the energy of the electron beam, the amount of H2 adsorption and the temperature of a cold surface. The yield of neutral H2 amounted to several hundreds (H2/e) when the electron energy was 200 eV and the amount of H2 adsorption was 0.2 (H2/Xe). The results of this study provide practical data on the outgassing problem of a cryosorption pump.