title: Real-time observation of the spin-state mixing process of a micellized radical pair in weak magnetic fields by nanosecond fast field switching.
abstract: The singlet-triplet spin-state mixing process of a singlet-born radical pair confined in a sodium dodecyl sulfate (SDS) micelle was studied by observing the nanosecond switched external magnetic field (SEMF) effect on the transient absorption signals. A long-lived singlet radical pair is generated by the photoinduced bond cleavage reaction of tetraphenylhydrazine in an SDS micelle. Application of off-on type SEMF results in the increase of the free radical yield contrary to the decrease produced by an applied static magnetic field. The S-T mixing process in low magnetic field was observed by means of a delay-shift SEMF experiment. Observed incoherent mixing processes are explained in terms of the interplay between coherent hyperfine interaction and fast dephasing processes caused by the fluctuation of electron-spin interactions. Singlet-triplet and triplet-triplet dephasing rate constants are determined independently to be 2 x 10(8) and 0.2 x 10(8) s(-)1, respectively, by a simulation based on a modified single-site Liouville equation. This is the first direct observation of the incoherent spin-state mixing process at magnetic fields comparable to the hyperfine interactions of the radical pair.
authors.affiliation: Graduate School of Science and Engineering, Faculty of Science, Shizuoka University, 836 Oya, Surugaku, Shizuoka 422-8529, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Miura
authors.forename: Hisao
authors.initials: H
authors.lastname: Murai
mesh_terms: D000042:Absorption; D005609:Free Radicals / Q000737:chemistry; D006834:Hydrazines / Q000737:chemistry; D007700:Kinetics; D008280:Magnetics; D008823:Micelles; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013997:Time Factors
chemical_list: D005609:Free Radicals; D006834:Hydrazines; D008823:Micelles; C029424:hydrazine; D012967:Sodium Dodecyl Sulfate