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.