Mishra Debadarshini, LaForge Aaron C, Gorman Lauren M, Díaz-Tendero Sergio, Martín Fernando, Berrah Nora
Department of Physics, University of Connecticut, Storrs, CT, 06269, USA.
Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049, Madrid, Spain.
Nat Commun. 2024 Aug 6;15(1):6656. doi: 10.1038/s41467-024-49671-6.
Roaming is an unconventional type of molecular reaction where fragments, instead of immediately dissociating, remain weakly bound due to long-range Coulombic interactions. Due to its prevalence and ability to form new molecular compounds, roaming is fundamental to photochemical reactions in small molecules. However, the neutral character of the roaming fragment and its indeterminate trajectory make it difficult to identify experimentally. Here, we introduce an approach to image roaming, utilizing intense, femtosecond IR radiation combined with Coulomb explosion imaging to directly reconstruct the momentum vector of the neutral roaming H, a precursor to formation, in acetonitrile, CHCN. This technique provides a kinematically complete picture of the underlying molecular dynamics and yields an unambiguous experimental signature of roaming. We corroborate these findings with quantum chemistry calculations, resolving this unique dissociative process.
漫游是一种非常规的分子反应类型，在这种反应中，碎片并非立即解离，而是由于长程库仑相互作用而保持弱束缚状态。由于其普遍性以及形成新分子化合物的能力，漫游对于小分子中的光化学反应至关重要。然而，漫游碎片的中性特征及其不确定的轨迹使得通过实验识别它变得困难。在此，我们介绍一种用于成像漫游的方法，利用高强度飞秒红外辐射结合库仑爆炸成像，直接重建乙腈（CH₃CN）中中性漫游氢（形成的前体）的动量矢量。该技术提供了基础分子动力学在运动学上完整的图像，并产生了漫游明确无误的实验特征。我们用量子化学计算证实了这些发现，解析了这一独特离解过程。
