Experimental and theoretical study on the photoionization of styrene.
Experimental and theoretical study on the photoionization of styrene.
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DOI：
10.1002/jms.4967
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发表时间：
2023-07
期刊：
影响因子：
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通讯作者：
Huanhuan Wang;Mingqiang Huang;Hao‐lin Chen;Xiaobin Shan;Zhenya Wang;Fu-yi Liu;Liu-si Sheng
中科院分区：
文献类型：
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作者：
Huanhuan Wang;Mingqiang Huang;Hao‐lin Chen;Xiaobin Shan;Zhenya Wang;Fu-yi Liu;Liu-si Sheng
本研究利用真空紫外光同步辐射光源和反射飞行时间质谱仪(TOF-MS)研究了苯乙烯的光致电离和解离。结合G3B3理论计算，分析了分子离子的光电离质谱和效率曲线，确定了分子离子的电离能、碎片离子的出现能以及相应的解离途径。在苯乙烯的光电离质谱中观察到的主要离子峰对应于C8H8+、C8H7+和C6H6+。测得苯乙烯的电离能为8.46±0.03 eV，而C8H7+和C6H6+的出现能分别为12.42±0.03和12.22±0.03 eV，与理论值一致。苯乙烯分子离子光解的主要通道是苯离子的形成，而失去氢原子的解离通道是次要通道。根据实验结果和经验公式，计算出C8H7+、C8H6+和C6H6+的解离能分别为(3.96±0.06)、(4.00±0.06)和(3.76±0.06)eV。结合有关的热化学参数，确定了C8H8+、C8H7+、C8H6+和C6H6+的标准生成热分别为964.2、1346.3、1350.2和1327.0 kJ/m o l。在理论研究的基础上，用莱斯-拉姆斯佩格-卡塞尔-马库斯(RRKM)理论确定了控制苯乙烯解离反应过程的动力学因素。这为进一步研究大气和星际环境中苯乙烯的大气光氧化反应机理提供了参考。
This study employed a vacuum ultraviolet synchrotron radiation source and reflectron time-of-flight mass spectrometry (TOF-MS) to investigate the photoionization and dissociation of styrene. By analyzing the photoionization mass spectrum and efficiency curve alongside G3B3 theoretical calculations, we determined the ionization energy of the molecular ion, appearance energy of fragment ions, and relevant dissociation pathways. The major ion peaks observed in the photoionization mass spectra of styrene correspond to C8 H8 + , C8 H7 + and C6 H6 + . The ionization energy of styrene is measured as 8.46 ± 0.03 eV, whereas the appearance energies of C8 H7 + and C6 H6 + are found to be 12.42 ± 0.03 and 12.22 ± 0.03 eV, respectively, in agreement with theoretical values. The main channel for the photodissociation of styrene molecular ions is the formation of benzene ions, whereas the dissociation channel that loses hydrogen atoms is the secondary channel. Based on the experimental results and empirical formulas, the required dissociation energies (Ed ) of C8 H7 + , C8 H6 + and C6 H6 + are calculated to be (3.96 ± 0.06), (4.00 ± 0.06) and (3.76 ± 0.06) eV, respectively. Combined with related thermochemical parameters, the standard enthalpies of formations of C8 H8 + , C8 H7 + , C8 H6 + and C6 H6 + are determined to be 964.2, 1346.3, 1350.2 and 1327.0 kJ/mol, respectively. Based on the theoretical study, the kinetic factors controlling the styrene dissociation reaction process are determined by using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. This provides a reference for further research on the atmospheric photooxidation reaction mechanism of styrene in atmospheric and interstellar environments.