Collision-induced fundamental band of D 2 in D 2–N 2 and D 2–CO mixtures

Abstract

Enhancement spectra of the collision-induced absorption of the infrared fundamental band of D 2 in D 2–N 2 and D 2–CO binary mixtures were recorded at 298 K with an absorption cell of sample pathlength 105.2 cm . Five base densities of D 2 in the range 12–20 amagat and several total gas densities of the mixtures up to 130 amagat were used. The observed spectra show the usual characteristic dip near the band origin Q 1(0) of the Q branch with two well-resolved components Q P and Q R as well as the absorption peaks O 1(3), O 1(2) and S 1( J), J=0 to 4. Binary and ternary absorption coefficients of the band arising from collisions of the type D 2–X and D 2–X–X, where X stands for N 2 or CO, have been determined. The spectra are interpreted in terms of the overlap transitions Q ov( J), J=0 to 4 and the following quadrupolar transitions of D 2–N 2 and D 2–CO: O 1( J)(D 2)+ Q 0( J)(N 2/CO); Q 1( J)(D 2)+ Q 0( J)(N 2/CO); S 1( J)(D 2)+ Q 0( J)(N 2/CO) and Q 1( J)(D 2)+ S 0( J)(N 2/CO) with J=0 to 4 for D 2 and J=0 to 25 for N 2/CO. An analysis of the absorption profiles was carried out by assuming appropriate line shape functions for the short-range overlap and for long-range quadrupolar contributions. Characteristic half-width parameters δ d and δ c for the overlap-induced transitions and δ q for the quadrupole-induced transitions were obtained from the profile analysis. Although CO has a small permanent electric dipole moment, present analysis does not indicate any detectable contribution from the electric dipolar induction mechanism in D 2–CO mixtures.