Real-time spectroscopy of the excited-state excitons in porphyrin J-aggregates

The excited exciton (S-2-exciton originating from the second-excited state of the molecules) was studied by real-time spectroscopy with 30-fs pulses. The ultrafast dynamics due to the S-2-S-1 internal conversion process were clearly observed in the pump-probe signal. The signal was modulated by the coherent molecular vibrations with 241 +/- 4 cm(-1) and 319 +/- 4 cm(-1) frequencies. The phase of the oscillation indicates that not only the ground state but also the excited state contribute to the oscillatory signal. The excited-state wave-packet motion was explained by dynamic intensity borrowing mechanism from the S-2 reversible arrow S-0-transitions to the S-1 reversible arrow S-0-transitions.