Influence of molecular reorientation on electronic energy transfer between a pair of mobile chromophores: The stochastic Liouville equation combined with Brownian dynamic simulation techniques.

Abstract

An algorithm is developed in order to solve the stochastic Liouville equation describing energy transfer between a donor-donor pair of reorienting chromophores. The algorithm requires the fluctuating part of the Liouville equation in the form of trajectories. In this particular case the molecular reorientation of the chromophores was simulated by means of a Brownian dynamic simulation technique where each of the two molecules are allowed to undergo a restricted rotational diffusion in a cone potential. Numerical results are presented for the correlation function 〈\ensuremath{\chi}(t)\ensuremath{\chi}(0)〉, representing the probability that the initially excited donor still is excited at a later time t. Results are given for the weak or F\orster regime and for a simple case in the strong or slow motion regime. The time resolved fluorescence anisotropy r(t) is also calculated for different molecular reorientational rates and cone potentials.