We observed the ultrafast response of exciton (S1-exciton) and excited-exciton (S2-exciton) in one-dimensional J-aggregates of three-level porphyrin molecules by femtosecond pump–probe spectroscopy. The decay profiles of the nonlinear response can be fitted to a sum of instantaneous response and two exponential decay components with time constants of 1.3±0.1 and 40±1 ps. The former and latter were found to correspond to the lifetimes of S2- and S1-excitons, respectively. The origins of the nonlinearity were attributed to the following three contributions: (1) coherent effects between the pump and probe via one-photon virtual S1-exciton, (2) induced absorption of real S2-excitons generated by two photons, and (3) induced absorption of real S1-exciton.
No takes yet. Share an insight, caveat, or question.
Misawa et al. (1999) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: