Institute for Ion Physics and Applied Physics and Center for Biomolecular Sciences (CMBI), University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
J Chem Phys. 2021 Feb 21;154(7):074306. doi: 10.1063/5.0040045.
A comprehensive investigation of low-energy electron attachment and electron ionization of the nimorazole radiosensitizer used in cancer radiation therapy is reported by means of a gas-phase crossed beam experiment in an electron energy range from 0 eV to 70 eV. Regarding negative ion formation, we discuss the formation of fifteen fragment anions in the electron energy range of 0 eV-10 eV, where the most intense signal is assigned to the nitrogen dioxide anion NO . The other fragment anions have been assigned to form predominantly from a common temporary negative ion state close to 3 eV of the nitroimidazole moiety, while the morpholine moiety seems to act only as a spectator in the dissociative electron attachment event to nimorazole. Quantum chemical calculations have been performed to help interpreting the experimental data with thermochemical thresholds, electron affinities, and geometries of some of the neutral molecules. As far as positive ion formation is concerned, the mass spectrum at the electron energy of 70 eV shows a weakly abundant parent ion and CHNO as the most abundant fragment cation. We report appearance energy (AE) measurements for six cations. For the intact nimorazole molecular cation, the AE of 8.16 ± 0.05 eV was obtained, which is near the presently calculated adiabatic ionization energy.
本文通过在电子能量范围为 0 eV 到 70 eV 的气相交叉束实验，对用于癌症放射治疗的尼莫佐尔增敏剂的低能电子附着和电子电离进行了全面研究。关于负离子形成，我们讨论了在 0 eV-10 eV 电子能量范围内形成的十五个碎片负离子，其中最强烈的信号分配给二氧化氮负离子 NO 。其他碎片负离子主要由硝基咪唑部分附近 3 eV 的共同临时负离子状态形成，而吗啉部分在尼莫佐尔的电子附加解离事件中似乎仅作为旁观者。量子化学计算已被用于帮助解释实验数据，包括热化学阈值、电子亲和力以及一些中性分子的几何形状。就正离子形成而言，电子能量为 70 eV 时的质谱显示出一个微弱丰富的母体离子和 CHNO 作为最丰富的片段阳离子。我们报告了六个阳离子的出现能 (AE) 测量值。对于完整的尼莫佐尔分子阳离子，获得的 AE 为 8.16 ± 0.05 eV，接近目前计算的绝热电离能。
