Knowledge Bank

The collision-induced 1st overtone infrared absorption band of deuterium has been observed at room temperature. The band was studied in the pure gas and in binary mixtures with argon and nitrogen at a path length of 194.3 cm at pressures up to 800 atm. The observed absorption profiles of the band do not show any splitting of the Q branch and this indicates that the contribution of the short range overlap forces to the intensity of the band is negligible. The enhancement absorption profiles of $D2$-Ar mixtures show only single-transition quadrupolar lines. But the enhancement profiles of $D2-N2$ mixtures, in addition, show the double transitions $Q2(J)$ of $D2+S0(J)$ of $N2$, and double vibrational transitions $Q1(J)$ of $D2+Q1(J)$ of $N2$ which occur on the low frequency side of the pure overtone band. Major contribution to the intensity of the absorption profiles of pure deuterium comes from the double transitions $Q2(J)+S0(J)$ and $Q1(J)+Q1(J)$ in the colliding pairs of $D2$ molecules. Integrated absorption coefficients were measured and binary and ternary absorption coefficients were derived. The observed enhancement absorption profiles of $D2-Ar$ and $D2-N2$ were analyzed by a computational procedure into their component lines to yield values of the characteristic half widths $\delta e$. The analysis of the profiles of $D2-Ar$ confirmed the fact that the contribution of the overlap forces to the intensity of the band is negligible. From the analysis of the pure overtone profiles of $D2-N2$, the contribution of the double transitions, $Q2(J)$ of $D2+S0(J)$ of $N2$, to the intensity of the band was estimated. The quadrupole moment of the nitrogen molecule was obtained as 1.14 $ea02$ from the ratio of the binary absorption coefficients of the band due to single and double transitions.