CIDEP measurement of the electron spin-lattice relaxation time of triplet benzophenone in liquid solution

Abstract

The relaxation of chemically induced electron polarization (CIDEP) in photoexcited triplet benzophenone is measured in competition with triplet quenching by 2,2′-azobis[isobutyronitrile] (AIBN). The spin polarization, transferred to the resulting 2-cyano-2-propyl radicals, is determined by time-resolved ESR spectroscopy for different AIBN concentrations. The rate constant for quenching is found to be k Q = 4.4 × 10 9 M −1 s −1, and 3 T 1 = 0.8 ns is obtained for the electron spin-lattice relaxation time of triplet benzophenone in 1,2-epoxypropane at room temperature.