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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Threshold Photoelectron-Photoion Coincidence Spectroscopy of Perfluorocarbons. 1. Saturated Perfluorocarbons C_2F_6, C_3F_8, and n-C_4F_(10)
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Threshold Photoelectron-Photoion Coincidence Spectroscopy of Perfluorocarbons. 1. Saturated Perfluorocarbons C_2F_6, C_3F_8, and n-C_4F_(10)

机译：全氟化碳的阈值光电子-光子符合光谱。 1.饱和全氟化碳C_2F_6，C_3F_8和n-C_4F_（10）

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Using vacuum-ultraviolet radiation from a synchrotron source, threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to study the decay dynamics of the valence electronic states of three saturated perfluorocarbon cations, C_2F_6~+, C_3F_8~+, and n-C_4F_(10)~+, in the energy range 12-25 eV. Electrons and ions are detected by threshold electron analysis and time-of-flight mass spectrometry, respectively, allowing breakdown diagrams showing the formation probability of fragment ions as a function of the internal energy of the parent ion to be obtained. The threshold photoelectron spectra of C_3F_8 and n-C_4F_(10) are reported for the first time in the literature. Higher resolution, fixed-energy TPEPICO spectra were also performed on some of the fragment ions, and the translational kinetic energy released in fragmentation was determined. By analysis of the breakdown diagrams of the three ions, nonstatistical effects were observed for states below 18 eV, indicating that decay takes place rapidly from these states before internal energy conversion can occur. This study indicates that impulsive decay can occur even for molecules with up to 14 atoms, implying that statistical decay cannot necessarily be expected even for large molecular species. Analysis of the mean kinetic energy releases also supports the suggestion that impulsive behavior is taking place for the fragmentation of C_2F_6~+ into C_2F_5~+ + F. For states above 18 eV, it is not obvious from this study whether decay is statistical or not. From the C_3F_8 study, new upper limits for the adiabatic ionization energy of the CF_3 radical (8.8 ± 0.1 eV) and the heat of formation of C_3F_7~+ at 298 K (-360 ± 20 kJ mol~(-1)) have been determined.
机译：使用同步辐射源的真空紫外辐射，使用阈值光电子-光子重合（TPEPICO）光谱研究了三个饱和全氟化碳阳离子C_2F_6〜+，C_3F_8〜+和n-C_4F_的价电子态的衰减动力学。 （10）〜+，在12-25 eV的能量范围内。通过阈值电子分析和飞行时间质谱分别检测电子和离子，从而获得分解图，该分解图显示了碎片离子的形成概率与母离子内部能量的函数关系。文献中首次报道了C_3F_8和n-C_4F_（10）的阈值光电子能谱。还对一些碎片离子进行了更高分辨率的固定能TPEPICO光谱分析，并确定了碎片中释放的翻译动能。通过分析这三个离子的分解图，可以观察到低于18 eV的状态的非统计效应，这表明在内部能量转换发生之前，这些状态会迅速发生衰减。这项研究表明，即使对于具有多达14个原子的分子，也会发生脉冲衰减，这意味着即使对于大分子物种，也不一定可以预期统计衰减。对平均动能释放的分析也支持以下暗示：正在发生脉冲行为，使C_2F_6〜+碎裂为C_2F_5〜++F。对于18 eV以上的状态，从这项研究中不知道衰减是否是统计的。根据C_3F_8研究，已经确定了CF_3自由基的绝热电离能的新上限（8.8±0.1 eV）和298 K（-360±20 kJ mol〜（-1））时C_3F_7〜+的形成热。决心。

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