Excited-state dynamics of rhodopsin probed by femtosecond fluorescence spectroscopy

Nonexponential fluorescence dynamics of bovine rhodopsin were measured at various wavelengths from 530 to 780 nm. No dynamic Stokes shift was detected but the fastest part of the fluorescence at both blue and red sides of the spectrum decayed faster than that at the center, which has led to the conclusion that the Franck-Condon state→fluorescence state conversion occurs within time-resolution of apparatus (<100 fs) owing to coupling with intra-chromophore high frequency modes and faster initial decay is due to sharpening of band shape caused by a decrease of amplitudes of hfm along the reaction coordinate of twisting.