Femtosecond study of S2 fluorescence in malachite green in solutions

By using femtosecond fluorescence spectroscopy, the relaxation kinetics of the second electronic excited state (S2) in malachite green has been investigated in several solvents with different viscosity. The decay time of the S2 fluorescence in water solution is obtained to be 0.27 ps and the internal conversion rate from the S2 state to the S1 state is estimated as (1.2 ps)−1. It has also been found that the S2 decay kinetics consists of fast and slow components in high-viscosity solvents. The S2 relaxation is explained in terms of the internal conversion and the torsional configuration change of molecules.