Resonance Raman spectra of ferri‐hemoglobin fluoride: Three scattering regimes

Abstract

Abstract Resonance Raman spectra have been obtained from dilute solutions of ferri‐hemoglobin fluoride, using several Ar + laser lines, as well as the 6328 Å He  Ne line, for excitation. Several modes (including some with inverse polarization) correspond to vibrations which mix the first two π – π* porphyrin transitions, and their excitation profiles confirm the assignment of the lower of these transitions to a band, at 5280 Å, which is unresolved in the room‐temperature absorption spectrum. Resonance enhancement of porphyrin modes with 6328 Å excitation suggests substantial mixing of the lower π – π* transition with porphyrin‐metal charge transfer transitions, which presumably account for the low energy visible bands. Totally symmetric modes are observed which come into resonance with the intense near‐ultraviolet (Soret) transition. The most intense of these, at 1373 cm −1 accurately obeys the frequency dependence expected for a mode which couples to a single electronic transition.