Kinetics of photochemical hydrogen abstraction in doped fluorene crystals studied by time-resolved optical nuclear polarization

Abstract

The rate of radical-pair formation in single crystals of fluorene doped with acridine resulting from a photoinduced hydrogen-transfer reaction has been determined between 145 and 300 K from the time development of the electron spin alignment in the radical-pair triplet state. The experimental technique described here is a newly developed pulse version of rf-induced optical nuclear polarization with time resolution to better than 10 −7 s. By comparison with the decay rate of the lowest acridine triplet state, it is shown that this state is the precursor of the photoreaction, in contrast to earlier reports.