Electron-impact high-lying N2− resonant states

Abstract

Quasibound states of the nitrogen molecular anion are studied by electron scattering from ${\mathrm{N}}_{2}$ using ab initio $R$-matrix theory and a close-coupling model. Scattering calculations are performed using both cc-pVTZ and cc-pVQZ target basis sets involving up to 26 low-lying target states in a complete active space configuration-interaction representation. Complex resonance potential energy curves are characterized as a function of internuclear separation for all eight ${{\mathrm{N}}_{2}}^{\ensuremath{-}}$ states identified, including the well-known $X{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Pi}}}_{g}$ shape resonance, one $1{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}_{g}^{+}$ Feshbach resonance, as well as six core-excited resonances involving 1 ${}^{2}{\mathrm{\ensuremath{\Delta}}}_{g}$, 1 ${}^{2}{\mathrm{\ensuremath{\Pi}}}_{u}$, 2 ${}^{2}{\mathrm{\ensuremath{\Pi}}}_{u}$, 3 ${}^{2}{\mathrm{\ensuremath{\Pi}}}_{u}$, 1 ${}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}^{+}$, and 1 ${}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}^{\ensuremath{-}}$. The ${}^{2}{\mathrm{\ensuremath{\Delta}}}_{g}$ and ${}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}^{\ensuremath{-}}$ resonant states are identified and characterized. Comparisons are made with the very different resonance structure in the isoelectronic ${\mathrm{CO}}^{\ensuremath{-}}$ anion. The present resonance analysis provides a starting point for studies of the vibrational excitation, electron-impact dissociation, and other resonance-driven phenomena in ${\mathrm{N}}_{2}$.