SPIN DYNAMICS OF NEUTRAL RADICAL PAIRS IN SINGLE-CRYSTALS OF DI-TERT-BUTYL-PYROCATECHOL DOPED WITH TETRAKIS(T-BUTYL)-PHENOXAZIN

The electron spin relaxation in radical pairs formed by photolysis of single crystals of 3,5-di-tert-butylpyrocatechol, doped with 10(-2) M 1-H-2,4,6,8-tetrakis(t-butyl)phenoxazine-1-one was studied by pulsed a nd stationary EPR in X-band in the temperature range 10-90 K. The rela xation patterns were partly biexponential and were interpreted within the frame of the four-level model of the radical pair, demonstrating t he importance of the singlet lever in the spin relaxation process. Ang ular dependencies of the characteristic relaxation times T-1 and T-2 w ere measured as well as the temperature dependence of T-1. In three ca ses asymmetric relaxation was found. Excitation spectra of the EPR sig nals show that different radical pairs (RP) may be distinguished by th eir action spectra.