Wc. Simpson et al., DISSOCIATIVE ELECTRON-ATTACHMENT IN NANOSCALE ICE FILMS - TEMPERATUREAND MORPHOLOGY EFFECTS, The Journal of chemical physics, 107(20), 1997, pp. 8668-8677
The electron-stimulated desorption (ESD) of D- ions from condensed D2O
films is investigated. Three low-energy peaks are observed which are
identified as arising from excitation of B-2(1), (2)A(1), and B-2(2) d
issociative electron attachment (DEA) resonances. A fourth, higher ene
rgy feature is also seen in the D- yield which is likely due to the fo
rmation of a transient anion state that dissociates and/or decays into
a dissociative excited state. The energies and ion yields of the reso
nances vary with the temperature and morphology of the D2O film. Below
60 K, the work function of the ice films changes with temperature and
the DEA resonances shift in energy. The D- ESD yield generally increa
ses with temperature, but it deviates from this trend at temperatures
corresponding to structural phase transitions in ice. The (B-2(1)) D-
temperature dependence is remarkably similar to that observed for the
ESD of low-energy D+ ions from D2O ice, even though the two originate
from different electronic excitations. These results are attributed to
thermally induced changes in the hydrogen bonding network, which chan
ges the lifetimes of the predissociative states that lead to ESD and w
hich also allows for the reorientation of surface molecules. (C) 1997
American Institute of Physics. [S0021-9606(97)02344-1].