Magnetic field dependent yield of geminate radical pair recombination in micelles. Effect of intraradical spin lattice relaxation

Jørgensen, Jørgen S.; Pedersen, J. Boiden; Shushin, A. I.

doi:10.1016/0301-0104(96)00176-0

Cited by 9 publications

(10 citation statements)

References 17 publications

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“…This effect happened due to an avoided crossing of the energy levels of the RP as a function of its orientation with respect to the magnetic field. The avoided crossing gives rise to maximal mixing of states and thus to a narrow dip (spike) in the singlet yield3940, while level crossing corresponds to zero mixing and thus to a narrow increase in the singlet yield40. Precisely this effect has been reported for a radical pair system with long lifetime which is, however, different from the effect discussed in the present investigation.…”

Section: Resultssupporting

confidence: 42%

Multiscale description of avian migration: from chemical compass to behaviour modeling

Pedersen

Nielsen

Solov’yov

2016

Sci Rep

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Despite decades of research the puzzle of the magnetic sense of migratory songbirds has still not been unveiled. Although the problem really needs a multiscale description, most of the individual research efforts were focused on single scale investigations. Here we seek to establish a multiscale link between some of the scales involved, and in particular construct a bridge between electron spin dynamics and migratory bird behaviour. In order to do that, we first consider a model cyclic reaction scheme that could form the basis of the avian magnetic compass. This reaction features a fast spin-dependent process which leads to an unusually precise compass. We then propose how the reaction could be realized in a realistic molecular environment, and argue that it is consistent with the known facts about avian magnetoreception. Finally we show how the microscopic dynamics of spins could possibly be interpreted by a migrating bird and used for the navigational purpose.

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Section: Resultssupporting

confidence: 42%

Multiscale description of avian migration: from chemical compass to behaviour modeling

Pedersen

Nielsen

Solov’yov

2016

Sci Rep

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“…The relaxation is assumed to be caused by the rotational modulation of the anisotropic hyperfine (hfi relaxation) and Zeeman interactions (∆g relaxation). The relaxation rate is given by the usual expression where ω ) gβB/p is the transition frequency of the electron spin, τ is the rotational correlation time of the radical, and the anisotropy parameters are defined as 20 Figure 1 shows the magnetic field dependence of the escape yield Y(B) for a model system similar to one considered previously. 8 Radical a has one magnetic nucleus with spin I ) Figure 2 is a replot of Figure 1 using a logarithmic scale for the magnetic field.…”

Section: High-field Resultsmentioning

confidence: 99%

“…The Supercage Model. The results of the previous articles ,, can be summarized as follows. The spin/space evolution of RPs within micelles can be divided into two stages: The first stage consists of an initial spatial separation of the RP within the micelle, and it ends with an equilibration of the spatial distribution due to multiple reflections from the boundary of the micelle.…”

Section: Theoretical Descriptionmentioning

confidence: 99%

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High-Field Supercage Model for Radical Pair Reactions in Micelles

Pedersen

Jørgensen

1997

J. Phys. Chem. A

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An analytic expression for the escape yield of a radical pair (RP) in a micelle under high magnetic fields is derived by the supercage model. This model is a two time scale model which divides the time evolution into two consecutive stages. The short time stage describes the initial separation of the partners of the RP, and the magnetic field dependence of the recombination yield can be described by the usual radical pair theory of freely diffusing radicals. The decay of a quasi-equilibrium during the second stage is described by rate equations for the spin density matrix, which for well-defined conditions can be reduced to a set of equations for the diagonal elements of the density matrix in the basis of true eigenstates of the Hamiltonian of the free radicals. In the present work we examine the applicability of the high-field limit of this approximation, which is closely related to the kinetic approach of H. Hayashi and S. Nagakura (Bull. Chem. Soc. Jpn. 1984, 57, 322). General analytic expressions for the magnetic field and relaxation dependence of the recombination yield during the second stage and for the decay constants are derived. The decay constants derived by H. Hayashi and S. Nagakura agree with our results. We show that the contribution from the first stage is significant and how it can be included.

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“…40 For instance, if the g tensor is axially symmetric, the time of relaxation due to spin rotational interaction in a strong magnetic field is given by , (26) where ∆g i = g i -2.0023 (i = ||, ⊥), r is the radius of the radical, k is the Boltzmann constant, T is temperature, and η is the viscosity of the solution.…”

Section: And Hc(o) • ) In Nonviscous Fluids Is Spin Rotational Relaxamentioning

confidence: 99%

Electron spin relaxation of radicals in weak magnetic fields

et al. 2006

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The review summarizes the results of studies on specific features of spin relaxation of radicals in liquids in weak magnetic fields.Key words: electron spin relaxation, weak magnetic field, free radicals, electron paramag netic resonance, spin polarization, chemically induced dynamic electron polarization.Many photochemical reactions involve radical stages. The interaction of external constant and alternating mag netic fields with electron and nuclear spins of intermedi ate radicals is the reason for the magnetic field and spin effects in radical chemical reactions. One of the key pa rameters determining the magnitude of the magnetic field effects is the spin relaxation rate of the intermediate radi cals. 1,2 In the case of long lived radical pairs (RPs), e.g., RPs in micellar solutions, 2 radical ion pairs, 3 biradicals, 4 etc., the spin relaxation is one of the main processes de termining the probability of RP recombination. The spin relaxation rate is an important parameter used in calcula tions of the magnetic field effect, 2 EPR spectra, 5 kinetics of chemically induced dynamic electron polarization (CIDEP), 1,6 optically detected EPR spectra, 3 stimulated nuclear polarization (SNP) spectra and kinetics, 7 etc. Usu ally, the magnetic field effects and the CIDEP, SNP, and optically detected EPR spectra are calculated assuming additive contributions of (i) electron relaxation in indi vidual radicals due to the interaction between an electron in a given radical and surrounding nuclei (modulation of anisotropic or isotropic HFI constant) or with the angular momentum of this radical (spin rotational relaxation) and (ii) dipole dipole and exchange relaxations due to the interaction between electrons in the radicals within the RP. Methods for the description of electron relaxation in the interacting radicals are not available as yet.To date, the electron spin dynamics and relaxation of free radicals have been well studied in strong magnetic fields that much exceed typical HFI constants of organic radicals. Various experimental techniques were elaborated and detailed theoretical concepts were proposed, which makes it possible to determine the spin relaxation rates by analyzing experimental data. 8, 9 Recently, there has been increasing literature on the behavior of radicals in weak magnetic fields whose magnitude is at most equal to the HFI constants of the radicals. Spin relaxation in weak magnetic fields has long been poorly studied both experi mentally and theoretically. Experimental studies are scarce because of relatively small number of methods of measur ing the relaxation times of radicals in weak magnetic fields. L Band time resolved EPR investigations of the radicals characterized by high HFI constants (30-70 mT) allow one to obtain information on the spin relaxation of radi cals in weak and zero magnetic fields. 10,11 Because the sensitivity of c.w. EPR in weak magnetic fields is low (~10 15 spins per sample), in this case information on elec tron spin relaxation can be extracted using indirect mag netic r...

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Magnetic field dependent yield of geminate radical pair recombination in micelles. Effect of intraradical spin lattice relaxation

Cited by 9 publications

References 17 publications

Multiscale description of avian migration: from chemical compass to behaviour modeling

Multiscale description of avian migration: from chemical compass to behaviour modeling

High-Field Supercage Model for Radical Pair Reactions in Micelles

Electron spin relaxation of radicals in weak magnetic fields

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