Charge transfer in collisions of C2+ ions with H atoms at low-keV energies:: A possible bound state of CH2+

Electron capture in C2++H collisions is studied theoretically by using a semiclassical molecular representation with nine molecular states for the doubler manifold at collision energies above 10 eW. The ab initio potential curves and nonadiabatic coupling matrix elements for the CH2+ 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) Sigma(+) state, but-a very shallow well in the 2 (2) Sigma(+) potential, suggesting a possibility of a bound state of CH2+. 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.