Collision-induced absorption by H2-H2 and H2-He pairs in the fundamental band - an experimental study.

Absorption coefficients for the collision-induced fundamental band of H₂, in the pure gas and interaction with He, have been measured at 298K between 3950 and 5300 cm^-1. The spectra were recorded with a 3-m long absorption cell for gas pressures up to 51 bar for pure H₂ and to 163 bar for H₂-He mixtures. In both cases, the authors have obtained new experimental results for the intercollisional interference Q(1) and S(1) dips, concerning essentially their width and their relative intensity. For pure H₂, the measurements of binary coefficients are in excellent agreement, except in the summit of the Q-branch (4200 cm^-1) and in the high frequency wing (ν ≥ 5200 cm^-1), with results from a recent ab initio quantum calculation. For H₂-He, the theoretical results at 300K arising from another recent quantum calculation are notably larger than the authors' experimental values over all of the spectral region under study.