Collision induced absorption spectra of the fundamental band of gaseous deuterium: Overlap parameters of D2–D2 collision pairs

Abstract

The collision induced absorption of the fundamental band of D2 in the pure gas was recorded for a number of gas densities up to 60 amagat at 77 and 196 K with a 2 m absorption cell and at 298 K with a 2.1 m absorption cell. Binary and ternary absorption coefficients of the band have been determined from the measured integrated absorption coefficients. An analysis of the absorption profiles was carried out by assuming appropriate line shapes and the halfwidth parameters δd and δc of the short-range overlap induced transitions and δq of the long-range quadrupole induced transitions have been determined. The profile analysis also made it possible to separate the contributions of these two types of transitions to the total intensity of the band. For the D2–D2 collision pairs, the overlap parameters λ and ρ, which represent the magnitude and range, respectively, of the overlap induced dipole moment, and μoverlap(σ), the overlap induced moment at the Lennard-Jones intermolecular diameter σ, have been determined; these are λ = 4.0×10−3, ρ = 0.21 Å, and μoverlap(σ) = 2.2×10−2 ea0 and are compared with those of the H2–H2 and HD–HD pairs derived from earlier work in our laboratory [S. P. Reddy et al., Phys. Rev. A 15, 975 (1977); S. P. Reddy and R. D. G. Prasad, J. Chem. Phys. 66, 5259 (1977)].