RAYLEIGH PEAK IN A MOLECULAR FLUID IN THE PRESENCE OF A TEMPERATURE-GRADIENT

The study of fluctuations around nonequilibrium steady states has shown a very interesting behavior when we calculate the density-density correlation function. In particular, the intensity of the Rayleigh peak is enhanced as a consequence of a resonant coupling between the heat mode induced on the system by external means and the transversal velocity modes. Here we consider a kinetic model for a molecular fluid, obtain the equations of motion, and calculate such an effect. Our results reproduce the calculated and measured characteristics of the spectra and show in an explicit way how the internal degrees of freedom in the molecule modify the structure factor.