Observation of molecular vibrations in the time domain with incoherent laser pulses

With the method of self-diffraction of incoherent light, molecular vibrations were observed in real time in various dye molecules pumped near the absorption edge. In Rhodamine 560, 35-fsec oscillations in the signal were measured, which corresponds to a vibrational frequency of 1000 cm(-1). Simultaneously, this technique can be used to deduce the ultrafast dephasing times in the molecular vibrational quasi-continuum. Dephasing times of 20 and 150 fsec were observed in Rhodamine 590 and Rhodamine 560, respectively.