Collison-induced absorption by H2-He pairs in the H2 fundamental band at 78 and 298 K.

Abstract

Measurements of collision-induced absorption spectra in the H[sub 2] fundamental band are reported for gaseous mixtures of hydrogen and helium at temperatures of 78 and 298 K and frequencies from about 3900 to 5200 cm[sup [minus]1]. Spectral line shapes are calculated from the fundamental theory with the isotropic interaction approximation, which has been successful in all previous comparisons of the kind for pure hydrogen and hydrogen--rare-gas mixtures. In the present case, however, the comparison of measured and calculated absorption profiles suggests that small differences between theory and measurement may exist for H[sub 2-]He in the H[sub 2] fundamental band, which are marginaly greater than the combined uncertainties of theory and measurement. Presumably, these are due to the neglect of the anisotropy of the interaction; the H[sub 2]-He system in the H[sub 2] fundamental band is more sensitive to the anisotropy of the interaction than the systems and bands studied previously.