PRESSURE NARROWING OF THE ROTATIONAL LINES IN THE FUNDAMENTAL INDUCED INFRARED ABSORPTION BAND OF H. IN $H_{2}-Ar, H_{2}-Kr$, AND $H_{2}-Xe$ GAS MIXTURES

$^{1}$J. De Remigis, J. W. Mactaggart and H. L. Welsh, Can. J. Phys. 49, 381 (1971). $^{2}$H. R. Zaidi and J. Van Kranendonk, Can J. Phys. 49, 385 (1971).""Author Institution: Department of Physics, University of TorontoIn a recent $publication^{1}$ the observation of a density-dependent narrowing of the quadrupole-induced rotational lines in the pressure-induced fundamental infrared band of hydrogen in $H_{2}-Ar$ gas and liquid mixtures was reported. It was found that for Ar densities greater than $\sim$300 amagat the half-width of the S (1) line of hydrogen varies inversely as the Ar density. Zaidi and Van $Kranendonk^{2}$ have interpreted this effect as a form of diffusional narrowing and have developed an expression for the half-width, $\Delta\nu_{1/2}$, in terms of the mutual diffusion coefficient of hydrogen in argon. In this paper the results of similar experiments on para-$H_{2}-Ar$, $H_{2}-Kr$, $H_{2}-Xe$, and pure $H_{2}$ are presented. In particular, the $S_{1}$ (O) line in $H_{2}-Ar$ exhibits the same density dependence as previously found for the $S_{1}$ (1) line. For $H_{2}-Kr$ and $H_{2}-Xe$ $\Delta\nu_{1/2}$ for the $S_{1}$ (1) line of $H_{2}$ varies inversely as the rare gas density for Kr and Xe densities greater than 380 and 246 amagat, respectively. By combining these results with the theory of Zaidi and Van Kranendonk the diffusion coefficients of $H_{2}$ in high density Ar, Kr and Xe gas are computed and found to compare favourably with the kinetic theory values