Femtosecond time-resolved Raman spectroscopy using stimulated Raman scattering

Femtosecond Raman spectroscopy has been developed to investigate ultrafast photoinduced structural changes of materials. Vibrational modes in the photogenerated transient species are measured by stimulated Raman scattering using a Raman pump pulse with narrow bandwidth and a femtosecond supercontinuum probe pulse. The Raman signal can be measured without slowing the temporal response and broadening the spectrum, because the temporal and spectral resolutions of the present method can be improved independently without the restriction of the transform limit. The transient Raman spectra of the trans- cis photoisomerization process in the DCM (4-dicyanomethylene-2-methyl-6-$p$-dimethylaminostyryl-4H-Pyran) dye solution were observed with the resolutions of 250 fs and $25{\mathrm{cm}}^{-1}.$