SIMPLE MODELING OF LINE-MIXING EFFECTS IN IR BANDS .2. NONLINEAR MOLECULES APPLICATIONS TO O-3 AND CHCLF2

A simple semiempirical approach is developed in order to model the sha pe of infrared absorption bands. It is based on use of the strong coll ision model and of a classical representation of rotational levels. Th e absorption coefficient then has a simple analytical expression whose wavenumber and pressure dependencies are computed by using eleven par ameters which depend on the considered vibrational transition, the tem perature, and the nature of the perturber only. These quantities, whic h are band-averaged values of the detailed spectroscopic and collision al parameters of the molecular system, can be deduced from direct fits of measured spectra. The model thus requires no previous knowledge of the characteristics of the molecules and is thus applicable to comple x systems; in particular it seems a promising approach for very dense molecular spectra for which only absorption cross sections are now ava ilable. Tests are presented in the case of O-3 and CHClF2 bands pertur bed by Nz at room temperature for which new measurements have been mad e. They demonstrate the accuracy of our semiempirical approach in pred icting the spectral shape in a wide range of density provided that eff ective parameters are used. (C) 1996 American Institute of Physics.