title: Open quantum system approach to the modeling of spin recombination reactions.
abstract: In theories of spin-dependent radical pair reactions, the time evolution of the radical pair, including the effect of the chemical kinetics, is described by a master equation in the Liouville formalism. For the description of the chemical kinetics, a number of possible reaction operators have been formulated in the literature. In this work, we present a framework that allows for a unified description of the various proposed mechanisms and the forms of reaction operators for the spin-selective recombination processes. On the basis of the concept that master equations can be derived from a microscopic description of the spin system interacting with external degrees of freedom, it is possible to gain insight into the underlying microscopic processes and  develop a systematic approach toward determining the specific form of the reaction operator in concrete scenarios.
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Technikerstrasse 21A, A-6020 Innsbruck, Austria. markus.tiersch@oeaw.ac.at
authors.forename: M
authors.initials: M
authors.lastname: Tiersch
authors.forename: U E
authors.initials: UE
authors.lastname: Steiner
authors.forename: S
authors.initials: S
authors.lastname: Popescu
authors.forename: H J
authors.initials: HJ
authors.lastname: Briegel