Photoionization of TMPD in DMSO solution: mechanism and magnetic field effects

Henbest, Kevin B.; Athanassiades, E.; Maeda, Kiminori; Kuprov, Ilya; Hore, P. J.; Timmel, Christiane R.

doi:10.1080/00268970600611017

Cited by 10 publications

(7 citation statements)

References 25 publications

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“…With these parameters, the low field effect in the exact QM calculation is seen to be quite pronounced, but not unreasonable: low field effects of this magnitude have certainly been observed experimentally. 34 As one would expect on the basis of the electron spin correlation tensors in Figs. 2 and 3, the present SC theory does a remarkably good job of capturing the correct low field effect, even in a radical pair with as few as 12 nuclear spins.…”

Section: The Low Field Effectmentioning

confidence: 70%

“…( 12) for a radical pair with no nuclear spins in one radical and 12 I = 1/2 nuclear spins in the other, as a function of the magnetic field strength B and the recombination rate constant k. The reason for taking one of the radicals in the pair to have no hyperfine interactions and the other to have many is that this has been established experimentally to be the situation in which the low field effect is most pronounced. 34,35 The reason for stopping at 12 I = 1/2 nuclear spins in the large radical is simply one of convenience: these calculations have to be done for a range of magnetic field strengths and for sufficiently long times to ensure the convergence of the integral in Eq. ( 12), and so are computationally more demanding than any of the calculations we have reported so far.…”

Section: The Low Field Effectmentioning

confidence: 99%

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An improved semiclassical theory of radical pair recombination reactions

Manolopoulos

Hore

2013

The Journal of Chemical Physics

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We present a practical semiclassical method for computing the electron spin dynamics of a radical in which the electron spin is hyperfine coupled to a large number of nuclear spins. This can be used to calculate the singlet and triplet survival probabilities and quantum yields of radical recombination reactions in the presence of magnetic fields. Our method differs from the early semiclassical theory of Schulten and Wolynes [J. Chem. Phys. 68, 3292 (1978)] in allowing each individual nuclear spin to precess around the electron spin, rather than assuming that the hyperfine coupling-weighted sum of nuclear spin vectors is fixed in space. The downside of removing this assumption is that one can no longer obtain a simple closed-form expression for the electron spin correlation tensor: our method requires a numerical calculation. However, the computational effort increases only linearly with the number of nuclear spins, rather than exponentially as in an exact quantum mechanical calculation. The method is therefore applicable to arbitrarily large radicals. Moreover, it approaches quantitative agreement with quantum mechanics as the number of nuclear spins increases and the environment of the electron spin becomes more complex, owing to the rapid quantum decoherence in complex systems. Unlike the Schulten-Wolynes theory, the present semiclassical theory predicts the correct long-time behaviour of the electron spin correlation tensor, and it therefore correctly captures the low magnetic field effect in the singlet yield of a radical recombination reaction with a slow recombination rate.

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Section: The Low Field Effectmentioning

confidence: 70%

Section: The Low Field Effectmentioning

confidence: 99%

An improved semiclassical theory of radical pair recombination reactions

Manolopoulos

Hore

2013

The Journal of Chemical Physics

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“…Although cryptochrome seems to be required for a number of magnetic responses in fruit flies [59][60][61][62][63][64][65][66][67][68] , there is no definite proof yet that cryptochrome functions as the magnetic sensor or that the Drosophila findings have a direct bearing on the mechanism of compass magnetoreception in birds. Moreover, it is not clear whether the magnetic field effects observed for purified cryptochromes in vitro 23,39,69 , or the reaction scheme that accounts for them, are identical to those in vivo 2 . It is therefore appropriate to explore alternative photocycles.…”

Section: Discussionmentioning

confidence: 99%

The sensitivity of a radical pair compass magnetoreceptor can be significantly amplified by radical scavengers

Kattnig

Hore

2017

Sci Rep

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109

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Birds have a remarkable ability to obtain navigational information from the Earth’s magnetic field. The primary detection mechanism of this compass sense is uncertain but appears to involve the quantum spin dynamics of radical pairs formed transiently in cryptochrome proteins. We propose here a new version of the current model in which spin-selective recombination of the radical pair is not essential. One of the two radicals is imagined to react with a paramagnetic scavenger via spin-selective electron transfer. By means of simulations of the spin dynamics of cryptochrome-inspired radical pairs, we show that the new scheme offers two clear and important benefits. The sensitivity to a 50 μT magnetic field is greatly enhanced and, unlike the current model, the radicals can be more than 2 nm apart in the magnetoreceptor protein. The latter means that animal cryptochromes that have a tetrad (rather than a triad) of tryptophan electron donors can still be expected to be viable as magnetic compass sensors. Lifting the restriction on the rate of the spin-selective recombination reaction also means that the detrimental effects of inter-radical exchange and dipolar interactions can be minimised by placing the radicals much further apart than in the current model.

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“…As far as the field-dependent detection of reaction products is concerned, one may restrict oneself to the final yield ϕ( B ) = c (∞, B ). The term MARY (magnetically-affected reaction yields) − spectra has become customary for the diagrams of such functions ϕ( B ). In a more general way, the functions c ( t , B ), when plotted against the field B for fixed values of time are denoted as time-resolved MARY spectra …”

Section: Introductionmentioning

confidence: 99%

J-Resonance Line Shape of Magnetic Field-Affected Reaction Yield Spectrum from Charge Recombination in a Linked Donor–Acceptor Dyad

et al. 2018

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Magnetic field effects (MFEs) allow detailed insight into spin conversion processes of radical pairs that are formed, for example, in all charge separation processes, and are supposed to play the key role in avian navigation. In this work, the MFE of charge recombination in the charge-separated state of a rigid donor–bridge–acceptor dyad was analyzed by a classical and a quantum theoretical model and represents a paradigm case of understanding spin chemistry with unprecedented detail. The MFE is represented by magnetic field-affected reaction yield (MARY) spectra that exhibit a sharp resonance, resulting from S/T level crossing as the Zeeman splitting equals twice the exchange interaction. Although in the classical kinetic model, the spin conversion processes between the four singlet and triplet substates are shown for the first time to obey an identical generalized energy dependence, quantum theory proves that the MARY resonance line is composed of relaxation, coherent hyperfine induced spin mixing, and S/T dephasing contributions.

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Photoionization of TMPD in DMSO solution: mechanism and magnetic field effects

Cited by 10 publications

References 25 publications

An improved semiclassical theory of radical pair recombination reactions

An improved semiclassical theory of radical pair recombination reactions

The sensitivity of a radical pair compass magnetoreceptor can be significantly amplified by radical scavengers

J-Resonance Line Shape of Magnetic Field-Affected Reaction Yield Spectrum from Charge Recombination in a Linked Donor–Acceptor Dyad

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