Quantum-resolved electron stimulated interface reactions: D-2 formation from D2O films

The low-energy (5-15 eV) electron stimulated desorption of D- and D-2 ((1)S igma(g)(+), upsilon = 0, J = 0 and upsilon = 1, J = 2) from condensed D2O f ilms is investigated as a function of substrate temperature. The D- ions ar e produced primarily via the B-2(1) dissociative electron attachment resona nce. Both the D- and D-2 yields are enhanced when the substrate temperature increases from 90 to 140 K. The changes in the D- and D-2 yields with subs trate temperature are qualitatively similar. We attribute the increase in y ields to thermally induced rotations or breaks in the near-surface hydrogen bonding network. This reduction in co-ordination and coupling reduces the nearest neighbor perturbations and enhances the surface or near surface exc ited state lifetimes. Production of vibrationally excited D-2 molecules cor relates with reactive scattering of D- at the surface, whereas production o f D-2 in the upsilon = 0 level also includes molecular elimination from an excited state which is produced by autodetachment. (C) 1999 Published by El sevier Science B.V. All rights reserved.