15min:

C. F. NIRO, J.-M. HARTMANN, C. BOULET, Laboratoire de Photophysique Moléculaire, C.N.R.S., Bât. 350, Université Paris-Sud, 91405 Orsay Cedex, France; AND F. HASE, Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung (IMK), P.O. Box 3640, D-76021 Karlsruhe, Germany.

While a number of studies have been devoted to the analysis of the far wings of the ₃ band lines of CO₂ near 4~µm those of the ₂ band have never been investigated although precise modeling of absorption in the 10--15~µm region is essential due to its importance for atmospheric sounding. Starting from the successful results obtained in the modeling of Q branch line mixing, the ECS (Energy Corrected Sudden) approach is extended in order to predict all line-mixing between P, Q, and R lines. The relaxation matrix is then constructed without use of any adjustable parameter for all CO₂ bands and with proper accounting of the coupling of angular momenta and of the symmetry of the vibrational transition. High pressure laboratory spectra have been recorded in the 600--1200~cm^-1 region for temperature condition spanning the typical atmospheric range (200--300~K). Comparisons with calculated values demonstrate the quality of the model which gives much better results than purely Lorentzian profiles. This result is confirmed when comparisons are made in the 4~µm region of the ₃ band wings. A compilation of first order coefficients derived from the relaxation matrix has then been used to compute atmospheric spectra. The comparison of calculated values with high-resolution ground based solar occultation spectra gives a further validation of our approach.