FT-EPR STUDY OF PHOTOIONIZATION IN MICELLAR SOLUTIONS

Fourier Transform EPR (FT-EPR) was used to study the formation and dec ay of free radicals produced by photoionization of phenothiazine (PTH) solubilized in aqueous SDS and Triton X-100 micellar solutions in the absence and presence of electron accepters. CIDEP spectra produced by PTH photoionization in micellar solution differ from those found in h omogeneous solution. The effect is attributed to changes in relative i mportance of single-photon, singlet excited state, and biphotonic, tri plet excited state, photoionization. With quinone accepters present in the bulk aqueous phase, photoionization of PTH in SDS, results in ins tantaneous formation of quinone anion radicals that carry the spin pol arization of the precursor hydrated electrons. If the acceptor is anch ored in the micelle, electron capture cannot compete with electron esc ape into the aqueous phase. Instead, anion radicals are formed primari ly by reductive quenching of (PTH)-P-3. This process gives rise to a spectrum that is attributed to long-lived spin-correlated radical pair s, [PTH+...Q(-)].