CF <sub>3</sub> Br和CF <sub>3</sub> I在电子散射中的形状共振和弹性截面,The Journal of Physical Chemistry A

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CF ₃ Br和CF ₃ I在电子散射中的形状共振和弹性截面
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-10-13 , DOI: 10.1021/acs.jpca.0c07845
M. B. Kiataki _{1,

2} , M. T. do N. Varella ₁ , M. H. F. Bettega ₂ , F. Kossoski ₃

Affiliation

三氟碘甲烷（CF ₃ I）与等标准气体（如三氟溴甲烷（CF _3）相比）具有许多有趣的优点，因此是基于等离子体技术的最有吸引力的候选材料之一Br）。低能电子易于将这些分子分解成反应性物质，而碰撞截面的知识对于在等离子体环境中模拟传输和反应性至关重要。尽管对与上述分子的电子碰撞进行了许多研究，但是在形状共振的分配和总横截面的大小方面存在矛盾的结果。在这里，我们尝试通过进行从头算电子散射计算来阐明这些方面。与以前的报告相比，我们发现与最新的测量结果完全一致的整体横截面。对于每一个分子，我们发现了一个σ _CX^*在CF共振（碳和重卤素之间反键）在1伏特₃ Br和在约0伏特在CF ₃I.此外，存在三个_σCF^*特征的形状共振。其中两个是简并的，并且在6 eV附近占了很大的比重，而另一个则出现在9.5 eV附近。我们还讨论了简并共振在解离电子附着反应中的可能作用，以及重卤素对横截面和形状共振的影响。

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Shape Resonances and Elastic Cross Sections in Electron Scattering by CF3Br and CF3I

Trifluoroiodomethane (CF₃I) is one of the most appealing candidates for applications in plasma-based technologies in view of its many interesting advantages when compared to more standard gases such as trifluorobromomethane (CF₃Br). Low-energy electrons are prone to decomposing these molecules into reactive species, and knowledge on the collision cross sections is fundamental for modeling transport and reactivity in plasma environments. Despite many studies on electron collisions with the abovementioned molecules, there are conflicting results on the assignment of shape resonances and on the magnitudes of total cross sections. Here, we try to clarify these aspects by performing ab initio electron scattering calculations. We found integral cross sections in fair agreement with the most recent measurements, in contrast to previous reports. For each molecule, we found a σ_CX^* resonance (antibonding between the carbon and the heavy halogen) at 1 eV in CF₃Br and at ∼0 eV in CF₃I. Furthermore, there are three shape resonances of σ_CF^* character; two are degenerate and account for a broad feature around 6 eV and the other one appears around 9.5 eV. We also discuss the possible role of the degenerate resonance in dissociative electron attachment reactions, as well as the impact of the heavy halogen on the cross sections and on the shape resonances.

更新日期：2020-10-22

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