PHOTODISSOCIATION OF CONDENSED CARBON-DIOXIDE BELOW THE GAS-PHASE THRESHOLDS

We have investigated photodesorption from condensed carbon dioxide for photon energies ranging from 13 to 35 eV using synchrotron radiation. We report the desorption of O-2(+) ions at energies as low as 13 eV, and discuss this behaviour in terms of ion-molecule reactions. The des orbed CO+ ion yield shows resonances at similar to 15.4 and similar to 17 eV, below the gas-phase thermodynamic threshold for CO+ formation. These peaks are also assigned to a two-step process, in which the pho todissociation of CO2 leads to neutral CO production. (C) 1998 Elsevie r Science B.V. All rights reserved.