Femtosecond relaxation dynamics in the electronic ground state of dye molecules studied by polarization-dependent amplification spectroscopy

A novel technique of time-resolved polarization spectroscopy permits the investigation of the ground-state dynamics of dye molecules in liquid solution. Relatively long vibrational relaxation times varying from 1.5 to 3.1 ps are reported for rhodamine 6G in different solvents. Evidence is presented for rapid intramolecular energy redistribution within the vibrational manifold on a time scale shorter than 100 fs. Analysis of the experimental data indicates that the dephasing of the vibronic transitions is mainly determined by these redistribution processes.