Low-frequency isotropic and anisotropic Raman spectra of aromatic liquids

摘要

The Raman spectra below 300 wavenumbers of six different aromatic molecular liquids have beennmeasured with a time and polarization resolved optical Kerr effect technique. The isotropic andnanisotropic contributions were determined to yield the complete third order response, and thus anmore detailed description of the microscopic liquid dynamics. The anisotropic contributionsnaccurately reproduced previously published results. Both the isotropic and anisotropic Ramannspectral densities shift toward lower frequencies with decreasing molecular weights. The firstnmoment of the isotropic spectral densities scales linearly with the inverse square root of thenmolecular weight, which is consistent with interaction-induced dynamics in these liquids beingndriven mainly by motions with a translational character. Also, the isotropic spectral densities couldnbe fit to a single Bucaro–Litovitz function. The exponent u0001 of this function increases monotonicallynwith the inverse square root of the molecular weight. A possible physical origin of this behavior isndiscussed.