Collision-induced absorption by H2 pairs in the second overtone band at 298 and 77.5 K:: Comparison between experimental and theoretical results

The collision-induced spectra of hydrogen in the region of the second overtone at 0.8 mu m have been recorded at temperatures of 298 and 77.5 K and for gas densities ranging from 100 to 800 amagats. The spectral profile defined by the absorption coefficient per squared density varies significantly with the density, so that the binary absorption coefficient has been determined by extrapolations to zero density of the measured profiles. Our extrapolated measurements and our recent ab initio quantum calculation are in relatively good agreement with one another. Taking into account the very weak absorption of the second overtone band, the agreement is, however, not as good as it has become (our) standard for strong bands. (C) 1999 American Institute of Physics. [S0021-9606(99)00310-4].