Emerging Nonvalence Anion States of [Isoprene-H·]·H2O Accessed via Detachment of OH–·Isoprene,The Journal of Physical Chemistry A

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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米/ 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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