Resonant Fragmentation of the Water Cation by Electron Impact: a Wave-Packet Study

Abstract

We have investigated the dissociation of a resonant state that can be formed in low energy electron scattering from H₂ O⁺ . We have chosen the second triplet resonance above the $\tilde{B}{}^{2}A{}^{\text{'}}$ $(\tilde{B}{}^2{B}_2)$ state of H₂ O⁺ whose autoionization mainly produces H₂ O⁺ ( $\tilde{X}{}^{2}A{}^{\text{'}}{}^{\text{'}}$ ). We have considered both dissociation of the resonant state itself, dissociative recombination (DR), or the dissociation of the H₂ O⁺ cation after autodetachment, dissociative excitation (DE). The time-evolution of a wave packet on the potential energy surfaces of the resonance and cationic states shows, for the initial conditions studied, that the probability for DR is about 38 % while the probability for DE is negligible.

Keywords: dissociative excitation; dissociative recombination; fragmentation of H2O+; fragmentation of water; resonant states.