Effect of high foreign-gas pressures on perpendicular and hybrid IR absorption bands for symmetric top molecules

ISSN： 0021-9037

Source： Journal of Applied Spectroscopy, Vol.74, Iss.1, 2007-01, pp. : 23-30

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Abstract

The effect of high foreign-gas pressure (He, Ar, N₂ up to 220 atm and CO₂ up to 90 atm) on the contours of perpendicular and hybrid IR absorption bands for symmetric top molecules has been studied. It has been established that over the entire studied pressure range, the shape of the contours of the perpendicular vibrational bands ν₄ and ν₅ for chloroform, deuterochloroform, and bromoform is stable and changes relatively little as the pressure increases. The effect of collisions on the band contours is estimated by comparing the contours for mixtures of compressed gases with the contours calculated in the approximation of the J-and M-diffusion models. It has been shown that intramolecular perturbation of free rotation by Coriolis forces is the determining factor in formation of the contours of the perpendicular bands, successfully competing with the perturbing effect of the foreign gases, evidence for which comes from the insignificant changes in the shape of the bands as the pressure of the foreign gases increases.