Theoretical models for interisomer transitions of complex molecules and their spectral manifestations

Abstract

We have used computer simulation to compare theoretical models for describing interisomer transitions of complex molecules and their spectral manifestations. We have shown that the kinetics of the intramolecular processes and time-resolved spectra, taking into account quantum beats between resonant (bound) states of the isomers (or isolated level subsystems for one isomer form), can be described not only by using a general molecular model in which the resonant levels of the subsystems act as a single level of a mixed state, with a time-dependent wave function in the form of quantum beats, but also by using a model interpreting the beat effect as a nonradiative transition. These models are completely equivalent: the parameters describing them have the same values, and numerical differences in the results obtained are no greater than 1% and are due to numerical round-off errors in the calculations and not differences between the models. The second model is preferred because it is graphically clear and conventionally used for describing and interpreting intramolecular processes, but it does take somewhat longer (∼10%) to run the simulation.