Raman spectral changes of neat CO2 across the ridge of density fluctuation in supercritical region

Density dependence of Raman spectra for carbon dioxide was studied along the isotherm in the temperature region 0.96⩽T/Tc⩽1.06 and the density region 0<ρ/ρc<2. Spectrum in the small-wavenumber region below 100 cm−1 and that in the region of the 2ν2 intramolecular band, i.e. one of the Fermi dyad, were carefully measured and analyzed. The results are interpreted by assuming the presence of the gas- and liquid-like regions in the supercritical region separated by the ridge of density fluctuation.