ELECTRONIC EXCITATION TRANSPORT AND TRAPPING IN MICELLAR SYSTEMS - MONTE-CARLO SIMULATIONS AND DENSITY EXPANSION APPROXIMATION

A theoretical treatment of electronic energy transport and trapping in a finite volume is presented by taking, as a typical example, an ensemble of chromophores solubilized in a spherical micelle. A truncated power series expansion in the chromophore density is used to calculate the configurational average of G(S)(t), the probability that an initially excited donor molecule is still excited, and G(D)(t), the probability of finding an excitation in the sub-ensemble of donors at time t, which are directly related to experimental observables. A detailed analysis of the problem via a Monte Carlo simulation is carried out for different occupation numbers of donor and trap molecules in a micelle, and for different ratios of the micelle radius to the Forster radius. The density expansion, as checked against the numerical results, provides a quite reasonable approximation, especially at short times and low chromophore concentrations. The difference in energy transfer dynamics between a finite and infinite volume system is described. The theory developed can be useful for probing structural details of microdisperse systems via time-resolved fluorescence measurements.