Unified approach to characterization of collisions between reactive radical pairs in solution. Final report

New techniques have been developed for accurately measuring time-dependent EPR spectra of small radicals produced by water radiolysis. These have been applied to the first systematic measurements of spin-lattice relaxation time for small radicals and prove a spin-rotation mechanism for these species. Heisenberg exchange and chemical decay rates for these species, and for the ''stable'' triphenylmethyl radical show that the former process is invariably diffusion controlled even when the latter is not. Initial EPR polarization has been documented for H atoms produced in radiolytic spurs and CIDNP has been detected from HD similarly formed. Both results indicate random spin orientation among initially formed H atoms in water radiolysis. A new mechanism for electron polarization has been discovered. This is a logical consequence of electron spin selective radical recombination and has been documented for sulfite radicals. An anomalous solvent dependence has been discovered for the carbon-13 hyperfine splitting of methyl radicals formed by photolysis of a diacyl peroxide. A technique has been developed for determining both the recombination rate constant and equilibrium association constant simultaneously for strongly associated free radicals using ESR exclusively. The technique has been applied to triphenylmethyl and gives results in good agreement with earlier data obtained by electronic spectroscopy