Luminescence measurements of Ar++H2O and N+2+H2O suprathermal charge transfer collisions: Product state distributions from H2O+Ã 2A1–X̃ 2B1 analysis

Abstract

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.