Excited-state diffusion-influenced reversible association–dissociation reaction: Brownian dynamics simulation in three dimensions

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Abstract
Excited-state diffusion-influenced reversible reaction, A * +B⇄C * , is investigated in three dimensions by suitably modifying the Brownian dynamics simulation algorithm of Edelstein and Agmon [J. Chem. Phys. 99, 5396 (1993)] which requires the exact Green functions of the geminate system. The proposed simulation algorithm is based on using the mixed look-up tables. For the excited bound state, the unimolecular decay is coupled to the reactive movement and its trajectory can be calculated with the aid of the excited-state look-up table. On the other hand, the unimolecular decay of the excited unbound state is assumed to be independent of the reactive movement and its trajectory is calculated with the ground-state look-up table. The optimum size of the time step is found by fitting simulations performed for the geminate case to the analytic result. The simulation results with varying concentration of B particles as well as the ratio of unimolecular decay constants are in excellent agreement with the kinetic theoretical predictions of Kwac et al. [J. Chem. Phys. 114, 3883 (2001)].