Lifetimes and Lifetime-Associated\nSpectra for Reversible\nExcited Two-State Reactions

Photoinduced excited-state processes have been platforms\nfor understanding\nthe molecular mechanisms of many chemical and biological reactions.\nTo elucidate associated chemical kinetics, time-resolved spectroscopic\nexperiments have been performed tracking how the populations of reactants\nand products change during the reactions while reaction conditions\nsuch as the concentration of a reactant, temperature, and solvent\nproperties change. Here, we simulate the lifetimes of a reactant and\na product, and construct their lifetime-associated spectra with the\nvarious combinations of rate constants based on the analytical solutions\nof differential rate equations. Depending on the combinations of the\nrate constants, the results diverge, which has often been overlooked\nin previous works. To demonstrate the validity of our approach, the\nresults are compared with the experimental results on diffusion-controlled\nexcited-state proton transfer. The presented global analysis simulation\ncan generally be applied to other excited two-state reactions.