Luminescence measurements of Ar++H2O and N+2+H2O suprathermal charge transfer collisions: Product state distributions from H2O+ A ̃ 2 A 1– X ̃ 2 B 1 analysis

Luminescence measurements of the Ar++H2O and N+2+H2O charge transfer systems are reported at collision energies ranging from 0.6 to 783 eV at a maximum resolution of 0.5 nm (FWHM). Both systems produce H2O+à 2A1–X̃ 2B1 emissions throughout the measured energy range. Approximate à state vibrational populations are determined using known spectroscopic constants. At the highest energies investigated, the à state population resembles a Franck–Condon distribution. At low collision energies, near-resonant vibrational levels of the à state are preferentially populated indicating dominance of large impact parameter charge transfer collisions. Population of high K vibronic sublevels, corresponding to high rotational excitation about the A rotational axis of H2O+, is observed in the nearest-resonant vibrational levels. A drop to near-zero population is observed for off-resonant levels at low collision energies that is associated with the dominance of the atom pickup channel at small impact parameters.