General transform technique for simultaneous frequency shifts and linear non-Condon coupling in resonance Raman scattering

• Published in: The Journal of chemical physics 1988-03, Vol.88 (6), p.3508-3515
• Main Authors: LU, H. M, PAGE, J. B
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; Molecular properties and interactions with photons; Molecular spectra; Physics
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.453898

The optical absorption→resonance Raman profile ‘‘transform’’ technique is generalized to the case of first-order profiles of modes having simultaneous linear non-Condon coupling and frequency shifts under electronic excitation. It is shown how the new transform follows, within well-defined approximations, from our recent general time-correlator analytic model expressions for the absorption and RR profiles of nonzero temperature multimode systems having both types of coupling. Mode mixing is assumed negligible for the Raman mode, but may be present for the remaining modes. It is found that the argument of the shift operators occurring in the transform is the Raman mode’s excited state frequency, in both the Condon and non-Condon terms. Moreover, it is shown that the Raman mode’s linear non-Condon and linear electron–phonon coupling constants are renormalized by the mode’s frequency shift. It is these model parameters which a transform analysis allows one to extract directly from measured absorption and profile data, a priori of explicit multimode modeling. Numerical illustrations of the new transform for a four-mode model system are presented, and the importance of including both non-Condon coupling and frequency shifts is demonstrated.