均匀瞬子理论用于桥介导的非绝热隧穿
Uniform instanton theory for bridge-mediated nonadiabatic tunneling
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中文总结 AI 辅助
本文提出均匀渐近瞬子理论，统一描述桥介导非绝热隧穿，解决高桥态区域理论失效问题，并应用于铁(II)配合物自旋跃迁研究。
中文摘要 AI 辅助
瞬子理论在路径积分框架内提供了非绝热速率常数的半经典近似，并捕获了隧穿和零点能等核量子效应。尽管最简单的反应直接从反应物进行到产物，但许多重要的非绝热过程涉及三个电子态，并通过虚拟桥态的协同机制反应，也称为桥介导隧穿或超交换。在先前的工作中，我们推导了一种瞬子理论来描述此类反应，使用在三个势能面上传播的主导隧穿轨迹。然而，这种方法仅在桥态能量足够低时有效。相反，在高桥态区域，桥面上的轨迹变得无限短，导致先前的理论失效。在本工作中，我们推导了高桥态区域的适当渐近近似，并发现所得理论简化为具有有效耦合的两态黄金规则瞬子，该耦合描述了到虚拟桥态的非共振跳跃。我们进一步发展了一种均匀渐近瞬子理论，消除了发散并平滑连接高桥态和低桥态区域。在配套论文中，我们将该方法应用于研究铁(II)配合物的五重态到单重态跃迁（通过三重态桥）。
英文摘要
Instanton theory provides a semiclassical approximation to nonadiabatic rate constants within a path-integral framework and captures nuclear quantum effects such as tunneling and zero-point energy. Although the simplest reactions proceed directly from reactants to products, a number of important nonadiabatic processes involve three electronic states and react via a concerted mechanism through a virtual bridge state, also referred to as bridge-mediated tunneling or superexchange. In previous work, we have derived an instanton theory to describe such reactions using a dominant tunneling trajectory that propagates on each of the three potential energy surfaces. However, this approach is only valid when the bridge state is sufficiently low in energy. In contrast, in the high-bridge regime, the trajectories on the bridge surface become infinitesimally short, which causes the previous theory to break down. In this work, we derive the appropriate asymptotic approximation for the high-bridge regime and find that the resulting theory reduces to a two-state golden-rule instanton with an effective coupling that describes a nonresonant hop to the virtual bridge state. We further develop a uniform asymptotic instanton theory that eliminates divergences and smoothly connects the high- and low-bridge regimes. In a companion paper, we apply the method to study the quintet-to-singlet transition (via a triplet bridge) of an iron(II) complex.
发表机构
- University of Bristol（布里斯托大学）
- ETH Zürich（苏黎世联邦理工学院）
- MPI for the Structure and Dynamics of Matter（物质结构与动力学马普研究所）
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