We discuss the averagetmatrix (ATA) and first passage time (FPT) approaches to excitation trapping. It is argued that the FPT involves unrealistic assumptions about the relative magnitudes of the donorndash;trap and donorndash;donor transfer rates. The ATA, which allows for arbitrary rates, does not have this defect. In three dimensions the ATA provides a useful description of the decay of excitation in the presence of a low concentration of traps. In lower dimensions the situation is unclear. In one dimension the ATA agrees with the asymptotic form of the exact solution for a periodic array of traps, whereas the FPT gives better agreement with exact results when the traps are randomly distributed.
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