Identification of Stable Perfluorocarbons Formed by Hyperthermal Decomposition of Graphite Fluoride Using Anion Photoelectron Spectroscopy
Identification of Stable Perfluorocarbons Formed by Hyperthermal Decomposition of Graphite Fluoride Using Anion Photoelectron Spectroscopy
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DOI：
10.1021/acs.jpcc.2c02180
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
Brett A. Williams;A. Siedle;C. Jarrold
中科院分区：
文献类型：
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作者：
Brett A. Williams;A. Siedle;C. Jarrold
利用阴离子光电子能谱（PE）表征了脉冲激光烧蚀氟化石墨（GF）产生的几种全氟化碳（PFC）物种，并将其与引入气相并带负电荷的PFC进行了比较。通过烧蚀GF产生的C6 F6-、C7 F8-和C5 F8-的PE光谱分别与通过电子附着到中性全氟化碳分子产生的六氟苯、全氟甲苯和全氟环戊烯的阴离子的PE光谱几乎相同。这一结果表明，激光烧蚀GF，这是一个超热分解事件，产生的物种大于CF2和稳定的分子结构。此外，阴离子PE光谱获得了几个较大的PFC分子阴离子，其中一些已经过去的计算研究的主题。这些物质的电子亲和力不能从宽PE光谱中明确确定，尽管使用系统方法来识别分离信号的开始以近似电子亲和力。全氟乙基环己烯的垂直脱离能为2.98 ± 0.05 eV。额外的全氟化碳自由基阴离子，包括全氟庚烯，全氟甲基环己烷，全氟-1，3-二甲基环己烷，和全氟萘烷的垂直脱离能，都超过3.495 eV。我们还表明，使用脉冲激光从氧化钆（Gd 2 O 3）的光电发射是一种高效和有效的方法，在气相中产生自由基阴离子的较大的挥发性分子。
Anion photoelectron (PE) spectroscopy was used to characterize several perfluorocarbon (PFC) species generated from pulsed-laser ablation of graphite fluoride (GF) and compare them to PFCs introduced into the gas phase and negatively charged by using a gentle photoemission source. The PE spectra of C6F6–, C7F8–, and C5F8–produced by ablation of GF are nearly identical with the PE spectra of the anions of hexafluorobenzene, perfluorotoluene, and perfluorocyclopentene, respectively, generated by electron attachment to the neutral perfluorocarbon molecules. This result suggests that laser ablation of GF, which is a hyperthermal decomposition event, produces species larger than CF2and with stable molecular structures. In addition, anion PE spectra were obtained for several larger PFC molecular anions, some of which have been the subject of past computational studies. The electron affinities of these species cannot be determined unambiguously from the broad PE spectra, though a systematic approach to identifying the onset of detachment signal was used to approximate the electron affinities. The vertical detachment energy of perfluoroethylcyclohexene was determined to be 2.98 ± 0.05 eV. The vertical detachment energies of additional perfluorocarbon radical anions, including perfluoroheptene, perfluoromethylcyclohexane, perfluoro-1,3-dimethylcyclohexane, and perfluorodecalin, all exceed 3.495 eV. We also demonstrated that photoemission from gadolinia (Gd2O3) using a pulsed laser is an efficient and effective method of generating radical anions of larger volatile molecules in the gas phase.