MANIFESTATIONS OF THE TRANSITION FROM THE EXCITED-STATE BY MEANS OF FEMTOSECOND 4-WAVE-MIXING SPECTROSCOPY

The influence of the transition from the excited state on the coherent transients of pump-probe measurements in a three-level system is disc ussed. A theoretical study related to a selective scheme of differenti al absorption pump-probe spectroscopy is performed in the framework of a full semiclassical description of the interaction of light and matt er. It is demonstrated how the coherent part of the modified signal ma y be used for detection of the up-transition from the excited state. A nnihilation processes characteristic of molecular aggregates at high p ump intensities are taken into account.