Moderately strong pump-induced ultrafast dynamics in solution

The transient transmittance spectra of laser dye IR144 in methanol were investigated experimentally in the moderately strong pump-probe field. Observed emission spectra in the red edge of the incident-field bandwidth, created by resonant impulsive stimulated Raman scattering (RISRS), display significant nonlinear intensity dependence as the pulse intensity increases. Dynamic perspectives of RISRS spectra can be understood well in a wavepacket picture. The excitation of high vibrational levels in the ground electronic state leading to the redshift of emissions presents high dependence of the pump-pulse intensity and ultrafast dynamical features, mapping the spatial overlap and separation of ground and excited wave functions and resolving the ultrafast vibrational relaxation in the femtosecond regime.