Lifetimes and Lifetime-Associated Spectra for Reversible Excited Two-State Reactions

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