Mauguière Frédéric A L, Collins Peter, Kramer Zeb C, Carpenter Barry K, Ezra Gregory S, Farantos Stavros C, Wiggins Stephen
School of Mathematics, University of Bristol, Bristol BS8 1TW, United Kingdom; email:
Department of Chemistry and Biochemistry, La Salle University, Philadelphia, Pennsylvania 19141; email:
Annu Rev Phys Chem. 2017 May 5;68:499-524. doi: 10.1146/annurev-physchem-052516-050613. Epub 2017 Mar 31.
In this review we discuss the recently described roaming mechanism for chemical reactions from the point of view of nonlinear dynamical systems in phase space. The recognition of the roaming phenomenon shows the need for further developments in our fundamental understanding of basic reaction dynamics, as is made clear by considering some questions that cut across most studies of roaming: Is the dynamics statistical? Can transition state theory be applied to estimate roaming reaction rates? What role do saddle points on the potential energy surface play in explaining the behavior of roaming trajectories? How do we construct a dividing surface that is appropriate for describing the transformation from reactants to products for roaming trajectories? How should we define the roaming region? We show that the phase space perspective on reaction dynamics provides the setting in which these questions can be properly framed and answered. We illustrate these ideas by considering photodissociation of formaldehyde. The phase-space formulation allows an unambiguous description of all possible reactive events, which also allows us to uncover the phase space mechanism that explains which trajectories roam, as opposed to evolving toward a different reactive event.
在本综述中，我们从相空间中非线性动力系统的角度讨论了最近描述的化学反应漫游机制。对漫游现象的认识表明，我们需要在对基本反应动力学的基本理解上进一步发展，这一点从考虑一些贯穿大多数漫游研究的问题中可以清楚地看出：动力学是统计性的吗？过渡态理论能否用于估计漫游反应速率？势能面上的鞍点在解释漫游轨迹的行为中起什么作用？我们如何构建一个适合描述漫游轨迹从反应物到产物转变的分界面？我们应该如何定义漫游区域？我们表明，反应动力学的相空间视角提供了一个框架，在这个框架中这些问题能够得到恰当的阐述和解答。我们通过考虑甲醛的光解离来说明这些观点。相空间公式允许对所有可能的反应事件进行明确的描述，这也使我们能够揭示相空间机制，该机制解释了哪些轨迹会发生漫游，而不是朝着不同的反应事件演化。
