Charge transfer in collisions ofC2+ions with H atoms at low-keV energies: A possible bound state ofCH2+

Abstract

Electron capture in ${\mathrm{C}}^{2+}+\mathrm{H}$ collisions is studied theoretically by using a semiclassical molecular representation with nine molecular states for the doublet manifold at collision energies above 10 eV. The ab initio potential curves and nonadiabatic coupling matrix elements for the ${\mathrm{CH}}^{2+}$ system are obtained from the multireference single- and double-excitation configuration interaction method. The adiabatic potential curves show no bound state for the $1{}^{2}{\ensuremath{\Sigma}}^{+}$ state, but a very shallow well in the $2{}^{2}{\ensuremath{\Sigma}}^{+}$ potential, suggesting a possibility of a bound state of ${\mathrm{CH}}^{2+}.$ The corresponding total and partial cross sections for charge transfer are found to be in a reasonable agreement with experiment in shape, but the present magnitude is found to be larger by nearly a factor of 2 at the high-energy end.