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Emerging Nonvalence Anion States of [Isoprene-H·]·H2O Accessed via Detachment of OH–·Isoprene
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-03-05 , DOI: 10.1021/acs.jpca.0c01250
Marissa A. Dobulis 1 , Michael C. Thompson 1 , Kellyn M. Patros 1 , Thomas Sommerfeld 2 , Caroline Chick Jarrold 1
Affiliation  

The anion photoelectron imaging spectra of an ion with m/z 85, generated under ion source conditions that optimize OH production in a coexpansion with isoprene, are presented and analyzed with supporting calculations. A spectroscopic feature observed at a vertical electron detachment energy of 2.45 eV, which dominates the photoelectron spectrum measured at 3.495 eV photon energy, is consistent with the OH·isoprene ion–molecule complex, while additional signal observed at lower electron binding energy can be attributed to other constitutional isomers. However, spectra measured over a 2.2–2.6 eV photon energy range, i.e., from near threshold of the predominant OH·isoprene detachment feature through the vertical detachment energy, exhibit sharp features with common electron kinetic energies, suggesting autodetachment from a temporary anion prepared by photoexcitation. The photon energy independence of the electron kinetic energy of these features along with the low dipole moment predicted for the neutral OH·isoprene van der Waals complex, suggest a complex photon-driven process. We present calculations supporting a hypothesis that near-threshold production of the OH···isoprene reactive complex results in hydrogen abstraction of the isoprene molecule. The newly formed activated complex anion supports a dipole bound state that temporarily traps the near zero-kinetic energy electron and then autodetaches, encoding the low-frequency modes of the dehydrogenated neutral isoprene radical in the electron kinetic energies.

中文翻译:

通过脱除OH ·异戊二烯获得的[Isoprene-H·]·H 2 O的新兴非价阴离子态

用离子的阴离子光电子光谱成像/ Ž 85,离子源的条件下生成的优化 OH生产符合异戊二烯coexpansion,呈现与辅助计算分析。在2.45电子伏特,其中占主导地位在3.495 eV的光子能量测定的光电子光谱,的垂直电子脱离能量观察到的光谱特征是与OH一致- ·异戊二烯离子-分子复合物,而附加信号在较低的电子观察到结合能可归因于其他宪法异构体。但是,光谱是在2.2–2.6 eV光子能量范围内测得的,即从主要OH –的阈值附近·异戊二烯通过垂直脱离能而具有的分离特征,具有通常的电子动能所具有的鲜明特征,这表明通过光激发制备的临时阴离子会自动分离。这些特征的电子动能的光子能量独立性以及为中性 OH·异戊二烯范德华复合物预测的低偶极矩,说明了一个复杂的光子驱动过程。我们提出的计算结果支持以下假设:OH···异戊二烯反应性络合物导致异戊二烯分子的氢抽象。新形成的活化的复合阴离子支持偶极结合态,该态暂时捕获接近零的动能电子,然后自动分离,在电子动能中编码脱氢中性异戊二烯自由基的低频模式。
更新日期:2020-03-05
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