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How quantum is radical pair magnetoreception?
Faraday Discussions ( IF 3.4 ) Pub Date : 2019-12-16 , DOI: 10.1039/c9fd00049f
Thomas P Fay 1 , Lachlan P Lindoy , David E Manolopoulos , P J Hore
Affiliation  

Currently the most likely mechanism of the magnetic compass sense in migratory songbirds relies on the coherent spin dynamics of pairs of photochemically formed radicals in the retina. Spin-conserving electron transfer reactions are thought to result in radical pairs whose near-degenerate electronic singlet and triplet states interconvert coherently as a result of hyperfine, exchange, and dipolar couplings and, crucially for a compass sensor, Zeeman interactions with the geomagnetic field. In this way, the yields of the reaction products can be influenced by magnetic interactions a million times smaller than kBT. The question we ask here is whether one can only account for the coherent spin dynamics using quantum mechanics. We find that semiclassical approximations to the spin dynamics of radical pairs only provide a satisfactory description of the anisotropic product yields when there is no electron spin-spin coupling, a situation unlikely to be consistent with a magnetic sensing function. Although these methods perform reasonably well for shorter-lived radical pairs with stronger electron-spin coupling, the accurate simulation of anisotropic magnetic field effects relevant to magnetoreception seems to require full quantum mechanical calculations.

中文翻译:

自由基对的磁感受如何量子化?

当前,迁徙鸣禽中最可能的磁罗盘感应机制取决于视网膜中成对的光化学形成的自由基的相干自旋动力学。自旋保守的电子转移反应被认为会导致自由基对,由于超精细,交换和偶极耦合,近简简的电子单重态和三重态状态相干地相互转换,并且对于罗盘传感器而言,至关重要的是塞曼与地磁场的相互作用。这样,反应产物的产率会受到比kBT小一百万倍的磁性相互作用的影响。我们在这里提出的问题是,是否只能用量子力学解释相干自旋动力学。我们发现,当没有电子自旋-自旋耦合时,自由基对的自旋动力学的半经典近似只能提供对各向异性产物产率的令人满意的描述,这种情况不太可能与磁感应功能一致。尽管这些方法对于寿命较短的自由基对具有更强的电子自旋耦合性能相当不错,但是与磁接收相关的各向异性磁场效应的精确模拟似乎需要完整的量子力学计算。
更新日期:2019-12-17
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