Quantum-Mechanical Calculation of the Intensity Distribution in Raman and Resonance Raman Spectra of a Phenylalanine Aqueous Solution

Quantum-mechanical calculations of the intensity distribution in the resonance Raman spectrum of an aqueous solution of phenylalanine, excited by light with wavelengths of 193, 204, 218, and 235 nm, and in the nonresonant Raman spectrum excited at a wavelength of 488 nm have been performed. The calculation results are in satisfactory agreement with the experimental data in the literature. Spectral lines characteristic of phenylalanine are observed, which can be used as markers when analyzing the peptide structure. It is noted that the contribution of highly excited electronic states (spaced by less than 10 eV from the resonant lines) to the scattering tensor components must be taken into account. The important role of the Herzberg-Teller effect in the description of spectral intensity distribution is demonstrated.