Collisional Quenching of Highly-Excited H₂ due to H₂ Collisions

Full text: Collisional energy transfer involving H₂ molecules are of significant interest, since H₂ is the most abundant molecular species in the universe. However, accurate calculations of collisional energy transfer in the H₂-H₂ system is still a challenging problem, especially for highly-excited H₂. Currently, most data are limited to initial rotational levels j≤ 8 or initial vibrational levels v≤ 3. The vast majority of these results involve some form of a reduced-dimensional approach which may be of questionable accuracy. Currently, we are extending the v=0 data to higher j using the accurate potential energy surface (PES) for the H₂ − H₂ system developed by Patkowski et al. and two quantum scattering programs (MOLSCAT and vrrmm). In order to solve the time-independent Schrodinger equation, the formalism for the scattering of two ¹Σ diatomic molecules described by Takayanagi and Green, and the close-coupling (CC) formalism of Arthurs and Dalgarno are employed. New inelastic quenching cross section for para-H₂+para-H₂ collisions with initial level v = 0, j = 10, 12 are shown. Calculations for other de-excitation transitions from higher initial levels are still in progress. Collisions involving other types of hydrogen ortho-H₂+para-H₂, ortho-H₂+ortho-H₂ and para-H₂+ortho-H₂ will be considered in the future. Other future work involves vibrational transitions with the full-dimensional PESs with full-dimensional scattering code TwoBC. (author)