Excitation energy transport between the ionic forms of rhodamine B in viscous solutions

Excitation energy transport between zwitterion and cationic form of rhodamine B in glycerol-ethanol mixture is studied. Concentration course of the quantum yield exhibits a rapid drop at intermediate concentrations, where no dimers are formed contrary to the results of measurements carried out for solutions with a trace amount of acid or base in which single ionic forms are adopted. To describe properly such concentration behavior of the quantum yield forward and reverse, nonradiative excitation energy transport between the forms is considered. This task is performed by comparing experimental data with Monte-Carlo simulations.