TY - JOUR

T1 - Evolution of spin coherence of radical pairs due to spin-selective recombination: Comparison of three models

AU - Bagryansky, Victor A

AU - Chetverikov, Artem O

AU - Borovkov, Vsevolod I

AU - Molin, Yuri N

N1 - This work was supported by the Russian Federal Ministry of Science and Higher Education (Grant No. FWGF-2021-0003). For the support of the development of the theoretical solution of the Jones and Hore model, V.I.B. and A.O.C. acknowledge the Russian Science Foundation (Project No. 21-13-00278). The authors are very grateful to A. B. Doktorov and K. M. Salikhov for productive discussions and to A. R. Melnikov for testing some results by computer simulations. We are also grateful to both reviewers for their comments, which significantly improved the manuscript. © 2023 Author(s). Published under an exclusive license by AIP Publishing.

PY - 2023/12/28

Y1 - 2023/12/28

N2 - This study looked for a way to evaluate the validity of previously suggested models for describing the spin-selective recombination of radical pairs. As an example, for analysis, we used the conventional model, the model by Jones and Hore [Chem. Phys. Lett. 488, 90 (2010)], and the model by Salikhov [Am. J. Phys. Chem. 11, 67 (2022)]. To do this, analytical solutions to the evolution of the radical pair density matrix due to a radical pair's spin-selective recombination and singlet-triplet transitions in a strong magnetic field were obtained for the conventional model and the Jones and Hore model. Spin interactions included in the Hamiltonian were time-independent exchange interactions as well as Zeeman and hyperfine interactions. The most striking difference between the models' predictions appeared when considering the fraction of singlet pairs among all currently existing ones. In the Jones and Hore model, this ratio has the form of damped oscillations for any values of the spin-hamiltonian parameters. The conventional model and the Salikhov model both predicted that this ratio had the form of undamped oscillations in the absence of exchange interaction and at a sufficiently low recombination rate. Besides, the conventional model predicts the possibility of a resonance-like behavior of this ratio when singlet-triplet transitions in a part of the radical pair ensemble are completely suppressed by tuning the magnetic field strength. Possible experimental conditions in which distinguishing between the models seems to be most straightforward were suggested.

AB - This study looked for a way to evaluate the validity of previously suggested models for describing the spin-selective recombination of radical pairs. As an example, for analysis, we used the conventional model, the model by Jones and Hore [Chem. Phys. Lett. 488, 90 (2010)], and the model by Salikhov [Am. J. Phys. Chem. 11, 67 (2022)]. To do this, analytical solutions to the evolution of the radical pair density matrix due to a radical pair's spin-selective recombination and singlet-triplet transitions in a strong magnetic field were obtained for the conventional model and the Jones and Hore model. Spin interactions included in the Hamiltonian were time-independent exchange interactions as well as Zeeman and hyperfine interactions. The most striking difference between the models' predictions appeared when considering the fraction of singlet pairs among all currently existing ones. In the Jones and Hore model, this ratio has the form of damped oscillations for any values of the spin-hamiltonian parameters. The conventional model and the Salikhov model both predicted that this ratio had the form of undamped oscillations in the absence of exchange interaction and at a sufficiently low recombination rate. Besides, the conventional model predicts the possibility of a resonance-like behavior of this ratio when singlet-triplet transitions in a part of the radical pair ensemble are completely suppressed by tuning the magnetic field strength. Possible experimental conditions in which distinguishing between the models seems to be most straightforward were suggested.

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85180899960&origin=inward&txGid=052be78b5e84ccb7ccfec0d2cdb7701d

U2 - 10.1063/5.0184479

DO - 10.1063/5.0184479

M3 - Article

C2 - 38149738

VL - 159

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 24

M1 - 244112

ER -