González-Vázquez Jesús, García Gustavo A, Chicharro David V, Bañares Luis, Poullain Sonia Marggi
Departamento de Química, Facultad de Ciencias, Universidad Autónoma de Madrid Spain.
Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid 28049 Madrid Spain.
Chem Sci. 2024 Jan 9;15(9):3203-3213. doi: 10.1039/d3sc04065h. eCollection 2024 Feb 28.
The valence-shell dissociative photoionization of methyl iodide (CHI) is studied using double imaging photoelectron photoion coincidence (i PEPICO) spectroscopy in combination with highly-tunable synchrotron radiation from synchrotron SOLEIL. The experimental results are complemented by new high-level calculations of the potential energy curves of the relevant electronic states of the methyl iodide cation (CHI). An elusive conical intersection is found to mediate internal conversion from the initially populated first excited state, CHI(), into the ground cationic state, leading to the formation of methyl ions (CH). The reported threshold photoelectron spectrum for CH reveals that the scissors vibrational mode promotes the access to this conical intersection and hence, the transfer of population. An intramolecular charge transfer takes place simultaneously, prior to dissociation. Upon photoionization into the second excited cationic state, CHI(), a predissociative mechanism is shown to lead to the formation of atomic I.
利用双成像光电子光离子符合（i PEPICO）光谱技术结合来自同步加速器SOLEIL的高度可调谐同步辐射，研究了碘甲烷（CHI）的价壳层解离光致电离。通过对碘甲烷阳离子（CHI）相关电子态势能曲线的新的高水平计算，对实验结果进行了补充。发现一个难以捉摸的锥形交叉点介导了从最初占据的第一激发态CHI（）到基态阳离子态的内转换，导致甲基离子（CH）的形成。所报道的CH的阈光电子能谱表明，剪刀振动模式促进了对该锥形交叉点的接近，从而促进了布居转移。在解离之前，分子内电荷转移同时发生。当光致电离到第二激发阳离子态CHI（）时，一种预解离机制导致了碘原子的形成。
