Collision-induced fundamental band of D2 in D2-N2 and D2-CO mixtures

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 D2 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 01(3), 01(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 D2N2 and D-2-CO: 01 (J)(132) + Q(0)(J)(N-2/CO); Q(1)(J)(132) + Q(0)(J)(N-2/CO); S, (J)(D2) + Q(0)(J)(N-2/CO) and Q, (J)(132) + So(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 delta(d) and delta(c) for the overlap-induced transitions and delta(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. (C) 2004 Elsevier Ltd. All rights reserved.