Spin-selective electron transfer reactions of radical pairs: Beyond the Haberkorn master equation
Spin-selective electron transfer reactions of radical pairs: Beyond the Haberkorn master equation
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自由基对的自旋选择性电子转移反应：Haberkorn主方程之外
DOI：
10.1063/1.5041520
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发表时间：
2018-08-14
影响因子：
4.4
通讯作者：
Manolopoulos, David E.
中科院分区：
文献类型：
--
作者：
Fay, Thomas P.;Lindoy, Lachlan P.;Manolopoulos, David E.
自由基对复合反应通常用电子和核自旋密度算符的量子力学主方程来描述。用Haberkorn反应项描述了主方程中电子自旋态选择性（单重态和三重态）复合过程。本文考虑一般的自旋态选择性电子转移反应，利用Nakajima-Zwanzig理论推导了自旋密度算符的主方程，从而阐明了非绝热反应速率理论与Haberkorn反应项之间的关系。对非绝热耦合的二阶微扰理论处理自然会得到带有附加反应标量电子自旋耦合项的Haberkorn主方程。这一项在以前的自旋化学计算中被忽略了，但我们表明它通常是相当重要的。我们还证明了在微扰理论的二阶以上，即在费米黄金法则极限之外，主方程中出现了一个额外的反应性单重态-三重态消相项。给出了反应性标量电子自旋耦合的马库斯理论参数的封闭表达式，该参数决定了单重态和三重态的复合速率。通过用精确的层次运动方程方法对自由基对反应进行模拟，我们证明了我们的主方程能够非常准确地描述发生自旋选择性非绝热电子转移反应的自由基对。反应性电子自旋耦合的存在很可能对生物相关的自由基对反应有影响，例如那些被认为在鸟类磁接受中起作用的反应。AIP出版社出版。
Radical pair recombination reactions are normally described using a quantum mechanical master equation for the electronic and nuclear spin density operator. The electron spin state selective (singlet and triplet) recombination processes are described with a Haberkorn reaction term in this master equation. Here we consider a general spin state selective electron transfer reaction of a radical pair and use Nakajima-Zwanzig theory to derive the master equation for the spin density operator, thereby elucidating the relationship between non-adiabatic reaction rate theory and the Haberkorn reaction term. A second order perturbation theory treatment of the diabatic coupling naturally results in the Haberkorn master equation with an additional reactive scalar electron spin coupling term. This term has been neglected in previous spin chemistry calculations, but we show that it will often be quite significant. We also show that beyond the second order in perturbation theory, i.e., beyond the Fermi golden rule limit, an additional reactive singlet-triplet dephasing term appears in the master equation. A closed form expression for the reactive scalar electron spin coupling in terms of the Marcus theory parameters that determine the singlet and triplet recombination rates is presented. By performing simulations of radical pair reactions with the exact hierarchical equations of motion method, we demonstrate that our master equations provide a very accurate description of radical pairs undergoing spin-selective non-adiabatic electron transfer reactions. The existence of a reactive electron spin coupling may well have implications for biologically relevant radical pair reactions such as those which have been suggested to play a role in avian magnetoreception. Published by AIP Publishing.