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(-)].