Dissociation Dynamics of Anionic Nitrogen Dioxide in the Low-Lying Resonant States.

Experimental studies of the dynamics near the molecular dissociation threshold are frequently frustrated, due to the small cross sections and the demand for identification of close-lying electronic states or nuclear motions with multiple degrees of freedom. Using the high-resolution anion velocity map imaging technique, here we report a dynamics study of the dissociations of anionic nitrogen dioxide in low-lying resonant states formed by electron attachment [e + NO (XA) → NO → NO (XΠ) + O (P)]. The long-term puzzling issues about the near-threshold dissociations of NO are settled. We suggest that three low-lying resonant states (B, B, and B) of NO contribute to the production of O at attachment energies of <5 eV. Furthermore, B and B symmetries of the resonant states lead to different anisotropies of the O angular distribution. At the relatively high electron attachment energies, a prompt fragmentation in the molecular bent conformation competes with an indirect dissociation in the straightened conformation.