Pulsed microwave irradiation effects on the dynamic behavior of a photochemically generated radical pair in a micellar solution

The radical pair dynamics in a photochemical hydrogen abstraction reaction of 2-methyl-1,4-naphthoquinone in a sodium dodecylsulfate micelle was modulated by a microwave pulse. After a short resonant 180 degrees microwave pulse, the recombination of the radical pair was enhanced, its rate constant being determined to be (8.3 +/- 0.8) x 10(6) s(-1). Other kinetic parameters were determined by the scanning of the microwave pulse position as follows: the formation of the radical pair (3.3 +/- 0.3) x 10(7) s(-1), the relaxation rate from the tripler (T+/-1) levels to the single-triplet (T-0) mixed one (3.3 +/- 0.3) x 10(5) s(-1) at 331 mT, and the radical escape rate (5.8 +/- 0.6) x 10(5) s(-1). (C) 1997 Elsevier Science B.V.