Mutual neutralization in low-energyH++H−collisions: A quantumab initiostudy

Abstract

The mutual neutralization of ${\mathrm{H}}^{+}$ and ${\mathrm{H}}^{\ensuremath{-}}$ at low collision energies is studied by means of a molecular close-coupling approach. All degrees of freedom are treated at the full quantum level also taking into account the identity of the nuclei. The relevant $^{1}\ensuremath{\Sigma}_{g}^{+}$ and $^{1}\ensuremath{\Sigma}_{u}^{+}$ electronic states as well as the associated nonadiabatic radial couplings are calculated for internuclear distances between 0.5 and $50{a}_{0}$. Following a transformation into a strictly diabatic basis, these quantities enter into a set of coupled equations for the motion of the nuclei. Numerical solution of these equations allows the cross sections for neutralization into the $\mathrm{H}(1)+\mathrm{H}(n)$, $n=1,2,3$ final states to be calculated. In the present paper, results are reported for the collision energy region $0.001--100\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, with special emphasis on the important energy region below $10\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The low temperature rate coefficient is obtained from a parametrization of the calculated cross section and is estimated to be valid over the range $10--10\phantom{\rule{0.2em}{0ex}}000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$.