Collision-induced 1st overtone infrared absorption band of deuterium.

The collision-induced 1st overtone infrared absorption band of deuterium was 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 half widths δs. 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 ea²₀ from the ratio of the binary absorption coefficients of the band due to single and double transitions