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.

Resonance Raman scattering study of azulene. I. Experiment and theoretical analysis via transform techniques A theoretical study of resonance Raman scattering from molecules. II. Temperature effect In a recent paper (Az I), well-structured T = 300 K resonance Raman (RR) profiles for the 1400, 1260,900, and 2X825 cm-I lines of azulene in CS 2 and for the 825 cm-I line of azulene in methanol were reported. Previously developed transform techniques were used to (1) compute RR profile line shapes directly from measured optical absorption spectra, and (2) extract ratios of Stokes loss parameters from the line shape scale factors. The transform analysis indicated that (1) our model assumptions (adiabatic and Condon approximations, harmonic phonons, atomic equilibrium position shifts, and small vibrational frequency shifts upon excitation to a single electronic state) are basically correct allowing for minor modifications, and (2) any deviations from these assumptions are likely to be larger for the 900 cm-I mode and smaller for the 1400 and 1260 cm-I modes. In this paper (Az II), we report model calculations of the optical absorption spectra, RR profile line shapes, and relative RR intensities. In these calculations, we use a recently proposed nonzero temperature multimode time-correlator modeling procedure. Compared with the conventional sum-over-states method, our time-correlator modeling procedure is superior in that (1) our optical absorption spectra and RR profiles computed via fast Fourier transform techniques have a practically unlimited spectral range and (2) the computing times are short for nonzero temperature multimode calculations. In our basic model, we adopt the assumptions of Az I and use seven azulene modes to obtain simultaneous good fits of the well-structured RR profile line shapes and optical absorption spectra. However, we find that the basic model does not account for the intensity of the 900 cm -I Raman line relative to that of the 1400 cm -I line, even though the individual profile line shape fits for these modes are very good. The basic model is therefore modified to allow mixing of the normal coordinates of these two modes. By introducing a single, relatively small mode-mixing parameter, we obtain a good fit of the relative RR intensities in addition to simultaneous detailed fits of the optical absorption spectra and RR profile line shapes. In an alternate approach, we modify our basic model and find that the inclusion of two relatively small non-Condon parameters, instead of one mode mixing parameter, can also produce simultaneous detailed fits of all of our optical absorption and RR data. A comparison of the two modified models solely on the basis of simplicity favors the mode-mixing model, since only one extra parameter is required to modify our basic model.

We have measured the pressure dependence of both the optical absorption and the resonance Raman (RR) excitation profiles of the breathing mode, v&, and its first two overtones for the substitutional impurity ion Mn04, in crystalline KC104. We have used the powerful transform technique of the time-correlator theory of RR scattering to analyze our RR data by calculating the profile line shapes directly from the measured optical absorption. This work constitutes the first successful application of the transform technique to the domain of high-pressure physics. The optical absorption displays a blue shift with increasing pressure, and both the groundand excited-electronic-state vibrational frequencies increase with pressure. We calculate the renormalized Stokes loss parameter of v, directly from ratios of the scaling factors used in fitting our calculated profile line shapes to the data. This "direct" transform method presumes the broadening mechanisms to be homogeneous, and it gives a decrease in the renormalized Stokes loss parameter of less than 10%%uo between one atmosphere and 10.6 GPa. We have also used a previously developed extension of the time-correlator theory to incorporate inhomogeneous broadening in the transform calculations. These calculations show that the effect of inhomogeneous broadening is not significant on the RR profile line shapes, but indicate that the decrease in the renormalized Stokes loss parameter with pressure could be as large as 15%.

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