Low-energy electron scattering ofNO:Ab initioanalysis of theΣ−3,Δ1, andΣ+1shape resonances in the local complex potential model

Abstract

We present an ab initio study of elastic scattering and vibrational excitation of $\mathrm{NO}$ by low-energy $(0--2.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ electron impact. The low-energy scattering cross sections are dominated by shape resonance contributions associated with the $^{3}\ensuremath{\Sigma}^{\ensuremath{-}}$, $^{1}\ensuremath{\Delta}$, and $^{1}\ensuremath{\Sigma}^{+}$ states of ${\mathrm{NO}}^{\ensuremath{-}}$. Resonance parameters for the three anion states were extracted from an analysis of fixed-nuclei variational (complex Kohn) calculations that employed elaborate trial wave functions. Independent estimates of the resonance parameters were obtained by analytically continuing the results of large-scale coupled-cluster calculations into the plane of complex momentum. The local complex potential model was used to calculate vibrational excitation cross sections, as well as the resonant portion of the vibrationally elastic cross sections. These results were combined with background contributions from the fixed-nuclei calculations to compute elastic and grand total cross sections. Our results capture the essential features of recent measurements of the cross sections, but suggest the need at lower energies for a more sophisticated, nonlocal treatment of nuclear dynamics.