Kinetic energy distributions for O- and metastable CO* produced by electron stimulated desorption from condensed CO2

We report kinetic energy (KE) distributions of O- anions and metastable CO* produced by 10-30 eV electron stimulated desorption from multilayer CO2 fi lms condensed on polycrystalline platinum at 20 K. The O- KE distributions are obtained from energy analysis with a hemispherical electrostatic deflec tor and the CO* KEs from time-of-flight measurements. Both anion and metast able energy distributions are broadened and the energy shifted is compared to those of the gas phase. The narrow (similar to 160 meV) and low energy ( similar to 60 meV) peaked CO* KE distributions reveal that post-dissociatio n interactions play a minor role in the broadening, whereas the wide (>1 eV ) KE distributions of O- result mainly from multiphonon excitation of the s ubstrate by the departing stable fragment anion. (C) 2000 Elsevier Science B.V. All rights reserved.