LINE-MIXING EFFECTS IN HE-BROADENED AND N-2-BROADENED SIGMA[--]II INFRARED Q BRANCHES OF N2O

Two Q branches of N2O near 579.3 and 2798 cm(-1) belonging to the 2 nu (2)(0e) - v(2)(1)f and nu(2) + nu(3) bonds, respectively, of Sigma<--P i and Pi<--Sigma symmetry, have been studied for He and N-2 pertubers at pressures ranging from 0.1 to 2 atm, using a tunable diode laser an d a difference-frequency laser spectrometer. To interpret the line-mix ing effects in these spectra, we have applied a model based on the ene rgy corrected sudden approximation whose parameters have been only der ived from Line-broadening data for N2O-He and also from the measured a bsorption by the Q branches for N2O-N-2. This model provides a satisfa ctory agreement with experimental band shapes, whatever the band, the perturber and the pressure considered. Significantly larger line-mixin g effects are shown for N2O-He with respect to N2O-N-2. Finally, the a ssumption made in the calculations to treat separately the couplings i n the even and odd j levels appears to have a negligible influence on the resulting band shapes. (C) 1998 American Institute of Physics. [S0 021-9606(98)00339-0].