ROTOTRANSLATIONAL COLLISION-INDUCED ABSORPTION BY H-2-H-2 PAIRS AT TEMPERATURES FROM 600-K TO 7000-K

The computation of the far-infrared, rototranslational (RT) collision-induced absorption (CIA) spectra of H-2-H-2 pairs is presented at temperatures from 600 to 7000 K for the first time. Theoretical results are based on the quantum mechanical and the semiclassical, three lowest translational spectral moments obtained for H-2 pairs. The effective, isotropic H-2-H-2 interaction potential, suitable for the high-temperature computations, and the ab initio induced dipoles, have been used as input. Special effort has been made to account for the rotational and vibrational states dependence of the dipoles, since it was found to be relevant at the high temperatures employed. The computations of the entire RT band account for all populated vibrational states of hydrogen molecule and include vibrational transitions upsilon --> upsilon' = upsilon, with upsilon = 0, 1, 2, and 3. The described method makes use of the adequately selected model line shapes with the temperature-dependent parameters. The presented model is useful for the ''model atmospheres'' of zero- and low-metallicity, cool and dense stellar atmospheres, where CIA is known to be important.