The collision-induced first-overtone band of hydrogen at low temperature

The collision-induced absorption spectrum of hydrogen in the region of the first overtone (8000 to 9000 cm-1) has been studied using a long path (110 m) at low temperature (28 K) and three different ortho-H2 - para-H2 ratios. An analysis of the band profiles shows that there is no evidence of an overlap-induced contribution in this region, and the standard theory of quadrupole-induced absorption overestimates the strength of the single vibrational band (Δν = 2) relative to that of the double vibrational band (Δν = 1 + 1) by a factor of 1.34. The Birenbaum -Cohen line-shape function gives a good fit to the observed spectra, and the parameters appearing in this function are well predicted by the work of Borysow et al. (22 refs., tab., 4 figs.)