Pressure-induced infrared absorption of the fundamental band of deuterium in D₂-He and D₂-Ne mixtures at different temperatures

Abstract

The pressure-induced fundamental infrared absorption band of deuterium in D₂-He mixtures at 77°K, 201°K and 273°K and in D₂-Ne mixtures at 77°K, 201°K, 273°K and 298°k was studied for gas pressures up to 600 atm for different base pressures of deuterium. The shapes of the enhancement absorption contours obtained in each case were discussed. The contours for D₂-He mixtures showed the splitting of the Q branch with the components QP and QR, the splitting being more pronounced at the higher temperatures. The quadrupolar lines S(0) and S(1) which appeared distinctly in the contours for D₂-Ne mixtures at 77°K were found to be absent in the corresponding contours for the D₂-He mixtures. Integrated absorption coefficients were measured and the binary and ternary absorption coefficients were derived. The theory of the "exp-4" model was applied to the binary absorption coefficients obtained experimentally. The quadrupolar parts of the binary absorption coefficients were calculated from the known molecular parameters and were then subtracted from the experimental values to obtain the overlap parts. The two overlap parameters λ and ρ, giving respectively the magnitude and the range of the overlap moment, were determined for each of the mixtures by fitting the calculated overlap part of the binary absorption coefficient as a function of the temperature to the experimental values of the overlap parts using a method of successive trials.