Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006 Madrid, Spain.
Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
J Phys Chem Lett. 2022 Aug 4;13(30):7001-7008. doi: 10.1021/acs.jpclett.2c01704. Epub 2022 Jul 27.
Low-energy electrons (LEEs) can very efficiently induce bond breaking via dissociative electron attachment (DEA). While DEA is ubiquitous, the importance of other reactions initiated by LEEs remains much more elusive. Here, we looked into this question by measuring highly accurate total cross sections for electron scattering from 1-methyl-5-nitroimidazole (1M5NI), a model radiosensitizer. The small uncertainty and high energy resolution allow us to identify many resonant features related to the formation of transient anions. In addition to novel insights about DEA reactions through the lower-lying resonances, our key finding is that the higher-lying resonances do not undergo DEA, implying alternative decay channels with significant cross sections. In particular, dissociation into two neutral fragments is probably involved in the case of 1M5NI. This finding has direct implications for the understanding of LEE-induced chemistry, particularly in the fundamental processes underlying the radiosensitization activity.
低能电子（LEEs）可以通过电子的离解吸附（DEA）非常有效地诱导键断裂。虽然 DEA 无处不在，但由 LEEs 引发的其他反应的重要性仍然更加难以捉摸。在这里，我们通过测量从 1-甲基-5-硝基咪唑（1M5NI）散射电子的高精度总截面来研究这个问题，1M5NI 是一种模型增敏剂。小的不确定性和高能量分辨率使我们能够识别许多与瞬态阴离子形成相关的共振特征。除了通过较低的共振获得关于 DEA 反应的新见解外，我们的主要发现是较高的共振不会发生 DEA，这意味着具有显著截面的替代衰减通道。特别是，1M5NI 可能涉及到分裂成两个中性片段的解离。这一发现对理解 LEE 诱导的化学过程具有直接影响，特别是在辐射增敏活性的基本过程中。
