Molecular dynamics of thiophene homologues investigated by femtosecond optical Kerr effect and low frequency Raman scattering spectroscopies

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Abstract
We present the results of femtosecond optical heterodyn detected optical Kerr effect(OHD-OKE)spectroscopy and low frequency Raman scatteringspectroscopy for three thiophene homologues ( C 4 H 4 X , X=O , S, and Se). The observed OHD-OKE transients were analyzed both in time and frequency domains. Fourier transformed OHD-OKE data were directly compared with the corresponding spontaneous Raman scattering spectra. The reorientation lifetimes for furan (O), thiophene (S) and selenophene (Se) were determined to be 0.9, 2.0 and 3.2 ps, respectively, and were fairly explained in terms of the Stokes-Einstein-Debye relation. Their subpicosecond dynamics was analyzed with an antisymmetric Gaussian function and a skewed function developed by Bucaro and Litoviz, which gave good curve fits to observed data. Librational and translational dynamics of the molecules was discussed in terms of microscopic environments formed by neighboring molecules and the results of intermolecular interaction energy calculations by an ab initio molecular orbital method.