Vibrational excitation cross section and V → T rate constants in molecular hydrogen

Vibrational excitation cross sections are computed for H₂ gas at various collision energies and between the lower-lying levels of the molecule. Only V → T processes are considered, while a quantum mechanical treatment via spherical potentials is implemented and applied. Various suggested potentials have been used and the corresponding results critically compared. The low-energy behaviour of the σ_{1 → 0} cross sections, and their orders of magnitude, appear to be in agreement with “experimental” deconvoluted data. Relaxation and excitation rates are computed and the K_1-0 (T) is examined over a wide temperature range to allow comparison with experiments. While the high temperature results are in fair agreement with the available data, the pure V - T mechanism of the present model seems to overestimate low-T rates as a consequence of the increase of (1 → 0) computed ross sections when bringing E_coll very near the lowest, υ = 1, threshold.