LINE-MIXING EFFECTS IN Q BRANCHES OF CO2 I - INFLUENCE OF PARITY IN DELTA[--]PI BANDS

A theoretical model based on the energy corrected sudden (ECS) approxi mation is used in order to account for line-mixing effects in Delta <- -> pi infrared Q branches of (CO2)-C-12-O-16. Its quality is demonstra ted by comparisons with numerous laboratory spectra of CO2-He and CO2- N-2 mixtures: three Q branches in the 4 and 17 mu m regions are invest igated at room temperature in a wide pressure range. The influence of mixing between Q(J) lines associated with odd and even values of the r otational quantum number J is demonstrated and analyzed in detail. It is shown that, in contrast to available fitting law approaches, the EC S model correctly predicts the influence of the parity of the rotation al quantum numbers J and J' on coupling between the Q(J) and Q(J') lin es. Comparisons between the effects of collisions of CO2 with N-2 and He are made and analyzed. They show that these two systems involve dif ferent line couplings within the Q branch. (C) 1997 Academic Press.