COLLISION-INDUCED FIRST OVERTONE BAND OF H-2 IN H-2-KR AND H-2-XE MIXTURES

Enhancement of the collision-induced absorption (CIA) spectra of the f irst overtone infrared band of H-2 in the H-2-Kr and H-2-Xe binary mix tures were recorded at 295 K for base densities of H-2 in the range 30 -57 amagat and for partial densities in the range 50-250 amagat far ea ch of Kr and Xe. The observed spectra consist of single transitions O- 2(J), Q(2)(J), and S-2(J) corresponding to the selection rule Delta J = -2, 0, and 2, respectively. Binary, ternary, and quarternary absorpt ion coefficients of the band arising from collisions of the type H-2-X , H-2-X-X, H-2-H-2-X, H-2-X-X-X, H-2-H-2-X-X, and H-2-H-2-H-2-X, where X represents Kr or Xe, have been determined from the integrated absor ption coefficients of the band. The spectra are interpreted in terms o f the quadrupolar induction mechanism and net evidence of the contribu tion from the isotropic overlap induction mechanism is found unlike in the CIA spectra of the fundamental band of H-2 [see S. P. Reddy, in P henomena Induced by Intermolecular Interactions, edited by G. Birnbaum (Plenum, New York, 1985), p. 129]. Analysis of the absorption profile s of the observed spectra was carried out using the Birnbaum-Cohen lin e-shape function [G. Birnbaum and E. R. Cohen, Can. J. Phys. 54, 593 ( 1976)] for individual components of the band and characteristic line s hape parameters were determined from the analysis. (C) 1997 American I nstitute of Physics.