Line broadening, line shifting, and line coupling effects on N2ndash;H2O stimulated Raman spectra

摘要

In order to understand the influence of H2O on the stimulated RamanQhyphen;branch spectra of nitrogen in combusting media, an exhaustive theoretical and experimental study has been carried out. Starting from a semiclassical model, particularly convenient at high temperature, theQhyphen;line broadening and shifting coefficients have been calculated over a wide temperature range and for a large number of lines. Stimulated Raman Spectra (SRS) measurements have allowed us to test these calculated line broadening coefficients and thus establish the high accuracy of semiclassical values. The theoretical broadening coefficients have been inverted to deduce statehyphen;tohyphen;state rotational relaxation rates by using two types of fitting laws. A partial test of the resultingQhyphen;branch profiles has been realized at moderate pressures leading to a discrimination between these two laws. Furthermore, the effect of rotational energy transfers on collisionally narrowed profiles at higher densities has been simulated and compared with the pure N2case.