Variational calculations of electron impact excitation of He near the2S3and2S1thresholds

Abstract

Matrix variational calculations, reported previously, of $e$-He inelastic scattering, have been extended into the near-threshold regions for excitation of the metastable states $2{}_{}{}^3{}_{}{}^{}S$ and $2{}_{}{}^1{}_{}{}^{}S$. Wigner cusp and rounded-step structures are computed at these thresholds for elastic and inelastic processes not involving the threshold channels. Excitation cross sections are computed for the threshold channels. The present computed results are compared with available experimental data, and found to be in general qualitative and quantitative agreement. A new estimate is derived of the rate coefficient for deactivation of $\mathrm{He}\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}S\right)$ by thermal electrons: a constant value 2.525 × ${10}^{-9\mathrm{}}$ ${\mathrm{cm}}^3$/sec for $T\le 1053$ °K.