Collision-Induced Absorption by H2 Pairs: From Hundreds to Thousands of Kelvin

An interaction-induced dipole surface (IDS) and a potential energy surface (PES) of collisionally interacting molecular hydrogen pairs H-2-H-2 was recently obtained using quantum chemical methods (Li, X.; et al. Computational Methods in Science and Engineering, ICCMSE. AIP Conf. Proc. 2009,; see also Li, X.; et al. Int. J. Spectrosc. 2010, ID 371201). The data account for substantial rotovibrational excitations of the H-2 molecules, as encountered at temperatures of thousands of kelvin (e.g., in the atmospheres of cool stars). In this work we use these results to compute the binary collision-induced absorption (CIA) spectra of dense hydrogen gas in the infrared at temperatures up to several thousand kelvin. The principal interest of the work is in the spectra at such higher temperatures, but we also compare our computations with existing laboratory measurements of CIA spectra of dense hydrogen gas and find agreement.