Quantum-mechanical analysis of the intensity distribution in spectra of resonant Raman scattering spectra of aqueous solutions of tyrosine

Abstract

Quantum-mechanical calculations of the intensity distribution in the resonant Raman scattering spectra of aqueous solutions of tyrosine excited by laser radiation with wavelengths of 244, 229, 218, 200, and 193 nm, as well as in the nonresonant Raman scattering spectrum excited at a wavelength of 488 nm, are performed. Satisfactory agreement is achieved between the calculation results and the experimental data. It is shown that the changes in the intensity distribution observed in the spectra with a change in the excitation wavelength from 244 to 193 nm correlate with the determined changes in the contribution made by excited electronic states into the scattering tensor components. It is noted that it is necessary to take into account the Herzberg–Teller effect and that the number of excited electronic states taken into account considerably affects the calculated relative intensities of lines. The possibility of existence of several tyrosine conformers in aqueous solution at room temperature is shown.