Line mixing effects in Q-branches of CO2 in helium near 4.7 mu m: A further test of the ECS formalism

We present experimental and theoretical results for the e-branches of the (12201<--01101) and (20001<--01101) bands of C-12 O-16(2) lying near 4.7 mu m perturbed by He. Measurements were carried out with the LPMA Fourier transform interferometer at room temperature and for atmospheric helium pressures. Computations, within the framework of the impact approximation, take into account line mixing effects. The relaxation matrix is modelled with the Energy Corrected Sudden (ECS) approximation derived from the Infinite Order Sudden (IOS) formalism proposed by Green [J. Chem. Phys. 90, 3603 (1989)] which is valid for all type of vibrational band. Strong deviations from the sum of the Lorentz shape are observed in the experimental spectra. The ECS calculations account for these experiments quite satisfactorily. (C) 1997 Elsevier Science Ltd.