Resonance raman spectra and excitation profiles of soret-excited metalloporphyrins

Resonance Raman spectra of nickel, chromium, and copper porphyrins, excited at their Soret maxima, show decreasing scattering intensity due to depolarized modes. This order correlates with diminished ¹Q(0-0) absorption in the porphyrins. The data are interpreted in terms of Jahn-Teller distortions in both Q and B states. General agreement between predicted and observed excitation profiles of nickel etioporphyrin I support a vibronic treatment of the excited states. The effect of tight focusing of the incident beam is to quench most Raman scattering intensity, except the 1384 cm^?1 line of the nickel complex.