Collision-induced microwave absorption in Ne–Xe and Ar–Xe gaseous mixtures

Abstract

Collision-induced microwave absorption has been observed at 4.4 cm−1 for the inert gas mixtures Ne–Xe and Ar–Xe. The absorption coefficient has been measured at room temperature for a range of density products up to 15 000 amagat2 and for different density ratios. The intracollisional absorption coefficient has been determined at this low frequency for each mixture from the data at low densities. These results for the absorption coefficient along with existing infrared results have yielded an accurate value for the zeroth moment for each of the spectra and hence improved values for the induced dipole moment parameters for the exponential model. For the range parameter, ρ, we obtain values of 0.312 Å and 0.408 Å, respectively, for the Ne–Xe and Ar–Xe mixtures. The values for the dipole strength parameters, μσ, calculated using the Lennard-Jones (12-6) potential are 0.0293 and 0.0328 D, respectively. Evaluations of μσ have also been carried out using other potentials. In particular, for Ne–Xe a value of μσ = 0.0377 D is calculated using the more realistic Morse – Spine – van der Waals (MSV) potential. At higher densities the results reveal intercollisional interference effects which result in a reduction of the absorption. The amount of reduction depends on the ratios of the gases in the mixture. In the highest density range studied, there is observed a marked increase in the absorption which may be attributed to many-body collisions.