REACTION YIELD DETECTED MAGNETIC-RESONANCE IN EXCIPLEX SYSTEMS .2. TIME RESOLVED AND PULSE STUDIES

In this paper are reported novel time dependent reaction yield detected magnetic resonance results from exciplex systems, obtained under continuous and pulsed microwave field conditions. One pulse sequence involves creating the exciplex in the absence of the microwave radiation, and then applying it in a continuous wave fashion during the period that exciplex fluorescence occurs. A second consists of creating the exciplex in the presence of this radiation. which is then removed during the observation period. The experiments yield extra insight into the kinetics of the spin correlated radial pairs in the systems over that reported in previous studies. The experiments have been analysed using a stochastic Liouville equation approach to the spin and molecular dynamics of the system, modelled substantially as a simple one-nucleus radical pair, and using both exponential and diffusional models of the kinetics. All the major features of the observations have been reproduced by one or other model. It has been confirmed that the radical pair lifetime is long (up to 300 ns) in the solutions studied, and it is suggested that the observations are affected by two different types of quantum beats, both occurring on previously unsuspected timescales.