LOW-ENERGY (5-120-EV) ELECTRON-STIMULATED DISSOCIATION OF AMORPHOUS D2O ICE - D(S-2), O(P-3(2,1,0), AND O(D-1(2)) YIELDS AND VELOCITY DISTRIBUTIONS

Laser resonance enhanced multiphonon ionization spectroscopy was used to measure yields and velocity distributions of the D(S-2), O(P-3(2,1,0)), and O(D-1(2)) produced during low-energy (5-120 eV) electron-beam irradiation of amorphous D2O ice. Electron-stimulated dissociation has a very low energy threshold (similar to 6-7 eV), and the neutral fragments desorb with low kinetic energies (similar to 60-85 meV) which are independent of the incident electron energy. The data suggest that desorption of neutral fragments results from dissociation of excited states formed directly or via electron-ion recombination.