Paramagnetic relaxation of radical cations in alkane solutions as measuredby time-resolved magnetic field effects

Spin-lattice relaxation times of radical cations were measured by the decay of the time-resolved magnetic field effect in the recombination fluorescen ce of radical ion pairs in liquid hydrocarbons at high concentrations of so lvent holes acceptor. The dependences of spin-lattice relaxation time on th e magnetic field strength and solvent viscosity were studied. The results c ould not be explained in terms of the model of ion-molecular charge transfe r involving monomeric or dimeric radical cations. The paramagnetic relaxati on observed in a weak magnetic field is attributed to internal reorganizati ons of aggregates that originate from radical cations at high acceptor conc entration.