THEORY OF DISPERSION OF RAMAN-SCATTERING BY MOLECULES CONTAINING 2 IDENTICAL CHROMOPHORES

It is shown that the interaction between identical chromophores of fre ely orienting rigid bichromophoric molecule described by the non-diago nal elements of the molecular damping matrix may lead to unusual dispe rsion of the depolarization ratios of Raman bands. The forms of the pr edicted dispersion curves depend on the mechanism for the occurrence o f a Raman band and on the mutual orientation of the chromophores. The dispersion curves have anomalous extrema at the frequency of the pure electronic transition of the molecule, i.e. at the maxima of the excit ation profiles of Raman lines in an examined frequency field, in contr ast to known dispersion curves of the depolarization ratio, the extrem a of which are often found to coincide with minims rather than maxima in the excitation profile. This circumstance favours the experimental observation of the predicted curves. Also presented is an excitation p rofile of the vibrational Raman optical activity signal for such rando mly oriented molecules with optically inactive chromophores. This prof ile has one sign only, unlike the. double-signed spectrum of circular dichroism for such molecules. This makes the recording of this profile under conditions of inhomogeneous broadening of spectral lines more c onvenient than recording the circular dichroism spectrum.