二甲醚在13.30～14.30 eV激发能下的光电离解离研究

doi:10.3969/j.issn.0253-2778.2020.05.010

摘要/Abstract

摘要： 利用同步辐射真空紫外光电离结合阈值光电子-光离子符合质谱技术对二甲醚分子在13.30～14.30 eV激发能下的电离-解离动力学进行了研究.该能量范围内，二甲醚离子处于B2B2和C2A2电子态，且两态相互重叠，解离产物则主要有m/z=45、29和31三种离子碎片.通过扣除重叠的m/z=29碎片离子质谱，获得了可靠的m/z=31碎片离子的飞行时间质谱轮廓.在此基础上，通过拟合质谱峰型获得了该碎片的平动能分布.在低于14.00 eV的范围内，该碎片离子仅表现出单一的统计解离通道性质，而当激发能量高于14.00 eV时，解离机理发生了明显的改变，表现出双模分布的特征.结合实验测量的平动能分布和理论预测结果，提出了不同电子态二甲醚离子解离产生m/z=31碎片离子的途径：B2B2电子态的二甲醚离子主要通过氢迁移异构化为CH2OHCH+3后解离生成CH2OH+(m/z=31)结构，而C2A2电子态则发生直接的C—O键断裂解离，生成高平动能分布的CH3O+(m/z=31)的碎片离子.

关键词: 光电子-光离子符合, 飞行时间质谱, 解离动力学, 反应机理

Abstract: Dissociative photodissociation of dimethyl ether in the photon energy of 13.30～14.30 eV was studied using threshold photoelectron photoion coincidence mass spectrometry, combined with photoionization using a vacuum ultraviolet light source from synchrotron radiation. In this range, the dimethyl ether ions in B2B2 and C2A2 states were prepared, and the main fragment ions were m/z=45, 29 and 31. By subtracting the contribution of the m/z=29 fragment ions, the reliable time-of-flight profile of the m/z=31 fragment ions was obtained. Then the related kinetic energy distribution was derived from fitting the profile. Below 14.00 eV, a unique statistical dissociation was observed for the formation of the m/z=31 ions, while the dissociation mechanism was changed significantly to dual dissociation

Key words: threshold photoelectron-photoion coincidence, time-of-flight mass spectroscopy, dissociation dynamics, reaction mechanism

中图分类号:

O643.1

徐磊，吴向坤，于同坡，周晓国，刘世林. 二甲醚在13.30～14.30 eV激发能下的光电离解离研究[J]. 中国科学技术大学学报, 2020, 50(5): 629-636.

XU Lei, WU Xiangkun, YU Tongpo, ZHOU Xiaoguo, LIU Shilin. Dissociative photoionization of dimethyl ether in the energy range of 13.3～14.3 eV[J]. Journal of University of Science and Technology of China, 2020, 50(5): 629-636.

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