Time-resolved fluorescence and absorption spectroscopies of porphyrin J-aggregates Available to Purchase

Dynamics of excited states in porphyrin J-aggregates has been investigated using femtosecond time-resolved fluorescence and absorption spectroscopies. An ultrafast relaxation process due to internal conversion (IC) from the $S2$-exciton state to the $S1$-exciton state is observed as an $S2$-fluorescence and a recovery from a bleaching of the $S2$-exciton state. The $S2$-fluorescence shows a sharp spectrum with almost no Stokes shift with a decay-time constant of $360±70 fs.$ In the transient absorption spectrum, the bleaching of the $S2$-exciton state disappears with a time constant of about 300 fs, which is in agreement with the result of the time-resolved fluorescence data. Relaxation dynamics of the $S1$-exciton following $S2→S1IC$ is also studied and several relaxation processes such as an intra-aggregate vibrational energy redistribution, vibrational and phase-space coolings are investigated.