Product state distributions for the C+(4P)+H2(D2) reaction from chemiluminescence spectra

Optical emission resulting from low-energy (1–3 eVc.m.) impact of metastable C+(4P) ions on H2 and D2 molecules has been studied spectroscopically in the 2700–3900 Å range. The b 3Σ−–a 3Π transition of CH+ (CD+) was resolved into numerous bands. From a spectrum simulation by computer, rotational–vibrational population distributions of the excited triplet state were obtained. In contrast to previous related studies, the vibrational excitation decreases with increasing collision energy. One-parameter surprisal fits of the vibrational (and, to a lesser extent, the rotational) population distributions are found to be unsatisfactory. The reaction is discussed in terms of changes of molecular orbital occupancy, which suggest a direct interaction mechanism. This is consistent with the observed population distributions.