A trajectory surface hopping study of the vibration-induced autodetachment dynamics of the 1-nitropropane anion.

In this study, we investigate the autodetachment dynamics of the 1-nitropropane anion after vibrational excitation of the energetically lowest C–H stretching mode using our recently developed extended quantum classical surface hopping approach including the detachment continuum. Therein the detachment from an electronic bound anion state is treated as a nonadiabatic transition into discretized detachment continuum states for an ensemble of classical nuclear trajectories propagated on quantum mechanical potential energy surfaces. The initial ensemble is obtained by sampling a phase space distribution accounting for the vibrational excitation of the C–H stretching mode of the molecule to match the experimental conditions. The simulated kinetic energy distribution of the ejected electrons reproduces characteristic features of the available experimental data. Analysis of the nuclear dynamics points out that the approach to neutral-like geometries with decreased pyramidalization angle of the NO 2 group and reduced the N–O bond lengths are the crucial factors enhancing the ultrafast autodetachment process in vibrationally excited 1-nitropropane. This is facilitated when the dipole-bound first excited state of the anion is populated, which is structurally similar to the neutral system. Although only a small transient population of this state is observed, it acts as an efficient doorway to the detachment continuum and is responsible for a significant amount of the ejected electrons. [ABSTRACT FROM AUTHOR]