Two-Dimensional Penning Ionization Electron Spectroscopy of NNO, HCNO, and HNNN: Electronic Structure and the Interaction Potential with He*(23S) Metastable and Li(22S) Ground State Atoms

Abstract

The electronic structure and Penning ionization of NNO, HCNO, and HNNN upon collision with He*(23S) metastable atoms were studied using He I photoelectron and two-dimensional Penning ionization electron spectroscopies (2D-PIES). From the peak shifts in PIES and collision energy dependence of partial Penning ionization cross sections, the interaction potentials between molecules and He*(23S) atoms were deduced. In the studied collision energy range, the interaction potential was found to be attractive around the nitrile oxide (−CNO) and azide (−NNN) groups, but no characteristic interaction was observed between NNO and He*(23S). Ab initio calculations on the similar interacting systems M−Li(22S) (where M = NNO, HCNO, and HNNN) at the CCSD/6-311++G** level revealed fine details of the anisotropy of the interaction potentials and were in good agreement with experimental results. The spectroscopic investigations predicted the existence of thermodynamically stable MLi radicals, and the structure and stability of HCNOLi and HNNNLi were calculated at the QCISD/6-311++G** level.