Dependence of H2O-N2 broadening coefficients on the vibrational quantum numbers

Line broadening in the case of H2O-N2 colliding system only slightly depend on vibrational quantum indices. The largest difference in the broadening coefficients of different bands is as small as several percent. Usually the halfwidths obtained for only one band is extrapolated to other vibrational bands. Indeed, in the case of low-lying states the vibrational amplitudes are usually small in comparison to the equilibrium distances between the atoms. However, for transitions to highly excited states, the intra-molecular motion cannot be treated as small amplitude vibrations, and as a consequence, corrections due to the intra-molecular interactions are large. The vibrational dependence of the line widths was studied by a high resolution Fourier-transform spectrometer IFS-125M. Line-broadening and line-shifting coefficients derived from the fitting were compared to calculated data.