Time-Resolved Optical Detection of Coherent Spin Motion for Organic-Radical-Ion Pairs in Solution

Abstract

The evolution of the singlet character of correlated ion radical pairs, prepared by high-energy impact in alkane solutions, is monitored by nanosecond-time-resolved solute-recombination fluorescence. Results obtained in the presence and absence of magnetic fields ($B<~4$ kG) show evidence for damped periodic modulations ($\ensuremath{\omega}\ensuremath{\approx}10$ MHz) of fluorescence intensity. They are explained in terms of hyperfine-interaction-induced coherent singlet-triplet mixing, and of field-dependent spin-lattice relaxation.