Kinetic Study of Triplet–Triplet Energy Transfer in Fluid Solution by Means of Laser Pulse Photolysis

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Abstract
The kinetics of triplet-triplet (T-T) energy transfer in fluid solution has been studied by means of laser pulse photolysis with acetophenone as the energy donor and naphthalene as the acceptor. Decay curves of phosphorescence of the donor and rise-and-decay curves of sensitized T-T absorption of the acceptor were obtained. These were analyzed to determine the unimolecular and bimolecular rate constants (denoted by k1 and k2 respectively) for the deactivation processes of the triplet state of donor or acceptor and the rate constant (kt) for the T-T energy transfer. In isooctane at room temperature these rate constants were found to be: k1=0.67×106 sec−1 and k2=2.0×1010 M−1 sec−1 for acetophenone, k2′=1.6×1010 M−1 sec−1 for naphthalene, and kt=1.0×1010 M−1 sec−1. The kt value obtained from the donor phosphorescence is in good agreement with that from the acceptor T-T absorption. The experimental results suggest that T-T transfer and T-T annihilation processes are not strictly diffusion-controlled.