Femtosecond relaxation processes from a higher excited electronic state of a dye molecule in solution

We have investigated the internal conversion and intramolecular energy redistribution process of coumarin 481 in cyclohexane after photoexcitation by a third harmonic of the Ti:Sapphire laser (267 nm). The fluorescence signals rise with time constants of 220–280 fs at all wavelengths and we do not find any drastic change of the spectral shape within a few picoseconds. These results suggest that the observed dynamics are mainly due to internal conversion from the Sn to S1 state and the intramolecular energy redistribution takes place much faster than the former process.