Unimolecular isomerisation of 1,5-hexadiyne observed by threshold photoelectron photoion coincidence spectroscopy
Unimolecular isomerisation of 1,5-hexadiyne observed by threshold photoelectron photoion coincidence spectroscopy
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阈值光电子光离子符合光谱观察1,5-己二炔的单分子异构化
DOI：
10.1039/d2fd00028h
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发表时间：
2022
影响因子：
3.4
通讯作者：
Osborn, David L.
中科院分区：
文献类型：
--
作者：
Savee, John D.;Sztáray, Bálint;Hemberger, Patrick;Zádor, Judit;Bodi, Andras;Osborn, David L.
本文用阈光电子能谱（TPE）研究了在高压极限下，3，4-二亚甲基环丁烯（DMCB）中间体（均为C6 H6）对炔丙基+炔丙基“头对头”加合物1，5-己二炔的单分子异构化反应。TPE光谱（TPES）记录与光电子光离子符合光谱使用同步真空紫外辐射。使用纯化合物或从热解数据中明智地提取的参考TPES用作热解定量的基函数。从这些光谱中，我们测量到8.401 ± 0.005 eV的修正富烯电离能。使用这些基函数分解温度依赖的热解光谱。基函数系数被转换为产品产量依赖于假设的积分阈值光电离截面获得的三个，部分互斥的假设集。因此，已经建立了DMCB、富烯和苯的产品产率以及它们的不确定性。导出的摩尔分数与基于C6 H6势和米勒和Klippenstein的RRKM主方程模型的建模一致[J. Phys. Chem. A，2003，107，7783]。尽管我们的结果与米勒和Klippenstein发现的苯和富烯的平行异构化途径完全一致，但我们观察到富烯的起始温度低于苯的起始温度，这与主方程模型一致，但与Stein等人的先前实验相反[Proc.Combust.仪器：1990，23，85]。这项工作促进了光离子质量选择阈值光电子能谱作为一种快速，灵敏，异构体选择性和定量检测工具之间的panoply建立的分析技术的使用。
The unimolecular isomerisation of the prompt propargyl + propargyl “head-to-head” adduct, 1,5-hexadiyne, to fulvene and benzene by the 3,4-dimethylenecyclobut-1-ene (DMCB) intermediate (all C6H6) was studied in the high-pressure limit by threshold photoelectron (TPE) spectroscopy. TPE spectra (TPES) were recorded with photoelectron photoion coincidence spectroscopy using synchrotron vacuum ultraviolet radiation. Reference TPES, obtained using pure compounds or judiciously extracted from the pyrolysis data, served as basis functions for pyrolysis quantification. From these spectra, we measured a revised fulvene ionisation energy of 8.401 ± 0.005 eV. Temperature-dependent pyrolysis spectra were decomposed using these basis functions. The basis function coefficients were converted to product yields relying on assumed integral threshold photoionisation cross sections obtained by three, partially mutually exclusive sets of assumptions. Thus, the product yields of DMCB, fulvene, and benzene have been established, as well as their uncertainty. The derived mole fractions are consistent with modeling based on the C6H6 potential and RRKM master equation model of Miller and Klippenstein [J. Phys. Chem. A, 2003, 107, 7783]. Although our results are fully consistent with the parallel isomerisation pathways to benzene and fulvene found by Miller and Klippenstein, we observe the onset of fulvene at a lower temperature than that of the onset of benzene, in agreement with the master equation model but in contrast to the previous experiments of Stein et al. [Proc. Combust. Inst., 1990, 23, 85]. This work promotes the use of photoion mass-selected threshold photoelectron spectroscopy as a rapid, sensitive, isomer-selective, and quantitative detection tool among the panoply of established analytical techniques.