Journal of Physical Chemistry A, Vol.108, No.51, 11165-11171, 2004
Fifth-order Raman spectroscopy of excited-state molecules
The fifth-order Raman spectroscopy of S-1 traps-stilbene in solution was demonstrated. A time domain observation of fifth-order Raman scattering was conducted by using ultrashort, tunable UV and visible pulses. A 22-fs UV pulse at 315 nm induced the first vibrational coherence state of the S-1 state. At the time delays of t(1) = 0.173, 0.216, 0.259, and 2.000 ps, a 17-fs visible pulse at 630 nm transferred the first coherence state to the second vibrational coherence state. The time-evolution of the second coherence state was probed by the other 17-fs visible pulse at 630 nm. Thirteen bands due to the fifth-order Raman scattering were identified in the Fourier transformation spectra of the second coherence in the range of 100-1300 cm(-1). The intensities and shapes of two bands at 193 and 398 cm(-1) showed significant t(1) dependence, whereas those of the other 11 bands were insensitive to t(1). The 193-cm(-1) band was assigned to the depletion of the UV-pump-induced first vibrational coherence (in-plane bending, nu(25)) by the first visible pulse. Both stepwise creation of the vibrational coherence of the overtone of the nu(25) mode and the depletion of the first vibrational coherence may have contributed to the 398-cm(-1) band. The 11 other bands are equivalents of time-resolved spontaneous Raman bands (third-order optical process) of S-1 traps-stilbene.