Energy transfer between two mobile chromophores in a zero energy transfer configuration. Cross-correlation effects in the fluorescence anisotropy r ( t )

Author： Fedchenia I.I. Westlund P.-O.

Publisher： Taylor & Francis Ltd

ISSN： 1362-3028

Source： Molecular Physics, Vol.84, Iss.1, 1995-01, pp. : 159-169

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Abstract

The energy transfer process between a pair of mobile chromophores has been determined by solving the stochastic Liouville equation numerically. The configurations of the chromophore pair were chosen in such a way that for the static case the energy transfer rate is zero. A restrictive molecular reorientation diffusion model is introduced in order to describe the reorientation of the chromophores. This motion introduces a fluctuating dipole-dipole coupling between the chromophores, and thus opens the energy transfer channel. We observe no qualitative difference between the relaxation behaviour of the time-correlation function 〈 X 1 ( t X 1 (0)〉 in the strong coupled or slow motion regime and the weak coupled or perturbation regime. ( X 1 ( t ) refers to the probability that the initially excited chromophores remains excited at time t .) This finding may introduce a serious complication when intermolecular distances are extracted from fluorescence anisotropy measurements. The absence of cross-correlation effects between the energy transfer process and molecular reorientation in the fluorescence anisotropy correlation function is also analysed in detail.