Knowledge Bank

The pressure-induced infrared absorption of the fundamental band of deuterium in $D2$-He mixtures at $77\circ K,201\circ K$ and $273\circ K$ and in $D2$-Ne mixtures at $77\circ K,201\circ K,273\circ K$ and $298\circ K$ was studied for gas pressures up to 600 atmospheres for different base pressures of deuterium. In the contours for $D2$-He mixtures, the splitting of the Q branch into the $QP$ and $QR$ components is more pronounced at higher temperatures. The quadrupolar lines $S(0)$ and $S(1)$ which appeared distinctly in the contours for $D2$-Ne mixtures at $77\circ K$ were not apparent in the corresponding contours for $D2$-He mixtures. Integrated absorption coefficients were measured and the binary and ternary absorption coefficients were derived. The absorption coefficients of the band for $D2$-He mixtures at $298\circ K$ were taken from the previous $work.1$ The theory of the ``exp-4'' $model2$ was applied to the experimentally obtained binary absorption coefficients. 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 $\lambda$ and $\rho$, giving respectively the magnitude and the range of the overlap moment, are 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.