title: Spin-selective recombination reactions of radical pairs: experimental test of validity of reaction operators.
abstract: Spin-selective reactions of radical pairs are conventionally modelled using an approach that dates back to the 1970s [R. Haberkorn, Mol. Phys. 32, 1491 (1976)]. An alternative approach based on the theory of quantum measurements has recently been suggested [J. A. Jones and P. J. Hore, Chem. Phys. Lett. 488, 90 (2010)]. We present here the first experimental attempt to discriminate between the two models. Pulsed electron paramagnetic resonance spectroscopy has been used to investigate intramolecular electron transfer in the radical pair form of a carotenoid-porphyrin-fullerene molecular triad. The rate of spin-spin relaxation of the fullerene radical in the triad was found to be inconsistent with the quantum measurement description of the spin-selective kinetics, and in accord with the conventional model when combined with spin-dephasing caused by rotational modulation of the anisotropic g-tensor of the fullerene radical.
authors.affiliation: Department of Chemistry, University of Oxford, Centre for Advanced Electron Spin Resonance, Inorganic Chemistry Laboratory, Oxford, United Kingdom.
authors.forename: Kiminori
authors.initials: K
authors.lastname: Maeda
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, 85287-1604 USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Liddell
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, 85287-1604 USA.
authors.forename: Devens
authors.initials: D
authors.lastname: Gust
authors.affiliation: Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, Oxford, United Kingdom.
authors.forename: P J
authors.initials: PJ
authors.lastname: Hore