FEMTOSECOND INVERSE RAMAN-SPECTRUM OF MOLECULAR J-AGGREGATES

The femtosecond inverse Raman spectrum of J-aggregates of a cyanine dy e was studied theoretically and experimentally by the pump-probe exper iment, The time dependence of the Raman signal intensity of the aggreg ates was fitted with an instantaneously responding component due to th e Stark effect together with 200 fs and 1 ps lifetime components due t o the excitons. The instantaneous response in the time-resolved differ ence transmission spectrum including the inverse Raman, induced and sa turated absorption was successfully reproduced by the calculation unde r sub-resonant excitation based on the density matrix formalism.