Ultra-fast dynamics in Coumarin 153 obtained by differential fluorescence

We present measurements of the molecular rotational diffusion dynamics in t he picosecond scale in a Coumarin 153 ethylene-glycol solution. A novel tec hnique is used in which the fluorescent sample is excited with two femtosec ond laser pulses in a pump and probe scheme. The spatial anisotropy generat ed by the first pulse excitation is sampled as a function of delay time thr ough the fluorescence produced by the delayed pulse. The rotational time is obtained from the change in the fluorescence produced as a function of the delay time. (C) 2001 Elsevier Science B.V. All rights reserved.