Low-Energy (5–120 eV) Electron-Stimulated Dissociation of AmorphousD2O Ice: D(2S), O(3P2,1,0), and O(1D2) Yields and Velocity Distributions

Laser resonance enhanced multiphonon ionization spectroscopy was used to measure yields and velocity distributions of the D $\left({}_{}{}^2{}_{}{}^{}S\right)$, O $\left({}_{}{}^3{}_{}{}^{}P_{2,1,0}^{}{}_{}{}^{}\right)$, and $\mathrm{O}\left({}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}\right)$ produced during low-energy (5–120 eV) electron-beam irradiation of amorphous ${\mathrm{D}}_2$O ice. Electron-stimulated dissociation has a very low energy threshold ( $\sim$6–7 eV), and the neutral fragments desorb with low kinetic energies ( $\sim$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.