Charge-transfer cross sections for radiative charge transfer inNa+H+andK+H+collisions at very low energies

Abstract

The total cross sections for radiative charge transfer in ${\mathrm{H}}^{+}+\mathrm{Na}(3s)\ensuremath{\rightarrow}\mathrm{H}(1s)+{\mathrm{Na}}^{+}$ and ${\mathrm{H}}^{+}+\mathrm{K}(4s)\ensuremath{\rightarrow}\mathrm{H}(1s)+{\mathrm{K}}^{+}$ collisions at energies below 8 eV have been calculated using an optical potential method. The relevant molecular states and molecular potentials were obtained by full configuration interaction calculations using pseudopotentials for the ion cores of Na and K. From the calculated charge-transfer cross sections, the radiative charge-transfer rate coefficients were obtained for temperatures below 10 000 K. The rate coefficients for both systems are found to have broad maxima around 20 K with values of the order of ${10}^{\ensuremath{-}12}{\mathrm{cm}}^{3}{\mathrm{s}}^{\ensuremath{-}1}.$ The rate coefficient for $\mathrm{Na}+{\mathrm{H}}^{+}$ remains nearly constant below the maximum, but that for $\mathrm{K}+{\mathrm{H}}^{+}$ decreases at lower temperatures. Both the rate coefficients and the differences between them decrease as the temperature increases beyond 20 K.