The Jahn–Teller (JT) distortion is one of the fundamental processes in molecules and condensed phase matters. For photoionized organic molecules with high symmetry, the JT effect leads to geometric instability in certain electron configurations and thus has a significant effect on the subsequent isomerization and proton migration processes. Utilizing the femtosecond pump–probe Coulomb explosion method, we probe the isomerization dynamics process of a monovalent cyclopropane cation (C₃H₆⁺) caused by proton migration and reveal the relationship between proton migration and JT distortion. We found that the C₃H₆⁺ cation evolves from the D_3h symmetric equilateral triangle geometry either to the acute triangle via two elongated C–C bonds (JT1) or to the obtuse triangle via a single elongated C–C bond (JT2). The JT1 pathway does not involve proton migration, while the JT2 pathway drives proton migration and can be mapped into the indirect dissociation channel of Coulomb explosion. The time-resolved experiment indicates that the delay time between those two JT pathways can be as large as ∼600 fs. After the JT distortion, the cyclopropane cation undergoes a subsequent structural evolution, which brings a greater variety of dissociation channels.

中文翻译：

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光离子化环丙烷中 Jahn-Teller 畸变和相关质子迁移的超快成像

杨-泰勒 (JT) 畸变是分子和凝聚相物质的基本过程之一。对于具有高对称性的光离子化有机分子，JT效应会导致某些电子构型的几何不稳定性，从而对后续的异构化和质子迁移过程产生显着影响。利用飞秒泵浦-探针库仑爆炸方法，探究了质子迁移引起的一价环丙烷阳离子（C ₃ H ₆ ⁺ ）的异构化动力学过程，揭示了质子迁移与JT畸变之间的关系。我们发现 C ₃ H ₆ ⁺阳离子从 D _3h对称等边三角形几何形状通过两个伸长的 C-C 键 (JT1) 演变为锐角三角形，或通过单个伸长的 C-C 键 (JT2) 演变为钝角三角形。 JT1途径不涉及质子迁移，而JT2途径驱动质子迁移，可以映射到库仑爆炸的间接解离通道。时间分辨实验表明，这两个 JT 路径之间的延迟时间可高达 ∼600 fs。 JT畸变后，环丙烷阳离子经历随后的结构演化，从而带来更多种类的解离通道。