Rayleigh and Raman scattering near the critical point of carbon dioxide

An experimental study of the behavior of depolarized Rayleigh and Raman spectra of carbon dioxide when approaching the critical temperature along the critical isochore is presented. The study of the depolarized Raman scattering was carried out on the Fermi diad ν1, 2ν2 and was supplemented by a study of the polarized Raman scattering. Contributions to the different physical mechanisms which can give rise to the depolarized spectra are carefully analyzed. We have shown that the orientational dynamics of CO2 molecules are unchanged by critical slowing down of the diffuse hydrodynamical mode associated to fluctuations of the order parameter in the range 0.01 °C