Line-mixing effects in He- and N2-broadened Σ⇆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<--Pi 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 and a difference-frequency laser spectrometer. To interpret the line-mixing effects in these spectra, we have applied a model based on the energy corrected sudden approximation whose parameters have been only derived from Line-broadening data for N2O-He and also from the measured absorption by the Q branches for N2O-N-2. This model provides a satisfactory agreement with experimental band shapes, whatever the band, the perturber and the pressure considered. Significantly larger line-mixing effects are shown for N2O-He with respect to N2O-N-2. Finally, the assumption made in the calculations to treat separately the couplings in the even and odd j levels appears to have a negligible influence on the resulting band shapes. (C) 1998 American Institute of Physics. [S0021-9606(98)00339-0].