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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electron Energy Loss and DFT/SCI Study of the Singlet and Triplet Excited States and Electron Attachment Energies of Tetramethylsilane, Hexamethyldisilane, Tris(trimethylsilyl)silane, and Tetramethoxysilane
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Electron Energy Loss and DFT/SCI Study of the Singlet and Triplet Excited States and Electron Attachment Energies of Tetramethylsilane, Hexamethyldisilane, Tris(trimethylsilyl)silane, and Tetramethoxysilane

机译：四甲基硅烷，六甲基二硅烷，三（三甲基甲硅烷基）硅烷和四甲氧基硅烷的单重态和三重态激发态的电子能量损失和DFT / SCI研究以及电子附着能

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摘要

Singlet and triplet excited States of the title compounds were investigated experimentally, using electron energy-loss spectroscopy (EELS), and theoretically, using density functional calculations that include configuration interaction (DFT/SCI). Both the triplet and the singlet spectra are well rationalized by the theory, permitting an assignment of the observed, broad bands and providing strong indication that DFT/SCI is suitable for the description of excited states in molecules containing third-row elements. The low-lying transitions in tetramethylsilane are found to be 4s and 4p Rydberg; the lowest valence states are higher, at9.8 eV (triplet) and 10.5 eV (singlet). The lowest triplet band in hexamethyldisilane is found to be valence, the upper orbital having πsymmetry. The lowest singlet state is 4s, albeit with zero oscillator strength. The lowest observed singlet band is 4p↓(xy) Rydberg with substantial π↑(*) valence admixture. The calculated density of excited states is high in tris(trimethylsilyl)silane, and Rydberg-valence mixing is prevalent. A high density of states is found also for tetramethoxysilane, the low-lying transitions being all Rydberg originating from the oxygen lone pair orbitals. Excitation functions for selected vibrational and electronically excited states are presented. The former provide the electron attachment energies. The latter indicate large cross sections for triplet excitation near threshold and, thus, imply substantial yield of triplet states under typical plasma conditions. The He I photoelectron spectrum of tetramethoxysilane is also presented.
机译：使用电子能量损失谱（EELS）对标题化合物的单重态和三重态激发态进行了实验研究，并在理论上使用了包括配置相互作用（DFT / SCI）的密度泛函计算进行了研究。该理论很好地合理化了三重态和单重态光谱，允许分配观察到的宽带，并提供有力的证据表明DFT / SCI适用于描述包含第三行元素的分子中的激发态。发现四甲基硅烷中的低位跃迁为4s和4p Rydberg。最低价态较高，分别为9.8 eV（三重峰）和10.5 eV（单重峰）。发现六甲基乙硅烷中最低的三重态带为化合价，上部轨道具有π对称性。最低的单重态为4s，尽管振荡器强度为零。观察到的最低单峰态带是4p↓（xy）Rydberg，具有大量π↑（*）价态混合。在三（三甲基甲硅烷基）硅烷中，计算出的激发态密度很高，并且里德堡价混合很普遍。还发现四甲氧基硅烷的状态密度很高，低位跃迁全部是赖德堡的起源于氧孤对轨道。给出了选定振动和电子激发态的激发函数。前者提供电子附着能。后者表示在阈值附近三线态激发的大横截面，因此暗示在典型的等离子体条件下三线态的大量产率。还给出了四甲氧基硅烷的He I光电子能谱。

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