Resonance Raman scattering study of azulene. I. Experiment and theoretical analysis via transform techniques

Abstract

Room temperature resonance Raman (RR) profiles for the 1400, 1260, 900 and 2×825 cm−1 lines of azulene in CS2 and for the 825 cm−1 line in methanol are reported. These profiles display pronounced multimode interference effects within the measured spectral range (570–720 nm). Using previously developed transform techniques, we analyze our RR data by calculating profile line shapes directly from our measured optical absorption data. The calculated and measured profile line shapes are in good agreement for all of the modes studied. These results are consistent with the model assumptions upon which the transform analysis rests. To further test our model assumptions, we extract ratios of the RR Stokes loss parameters from the scale factors of our profile line shape fits. RR Stokes loss parameters estimated from these ratios are found to be in good correlation with published 2K emission intensity ratios. However, their correlation with published 4K absorption intensity ratios indicates the presence of some intensity borrowing and hence implies deviations from our model assumptions. Nevertheless, the good line shape agreement for all of the modes studied, together with the lack of strong intensity borrowing, indicate that large deviations from our model assumptions are unlikely. The present study serves as a useful prelude for simultaneous modeling of the optical absorption spectra, the RR profile line shapes, and the RR relative intensities. Such model studies will be reported in a future publication.