Abstract

The photoionization and dissociative photoionization of o-xylene have been studied using synchrotron radiation vacuum ultraviolet light with the photon energy in the range of 8.0–13.0 eV. The ionization energy of o-xylene and the appearance energies for the main fragment ions \(\hbox {C}_{\mathrm {8}}\hbox {H}_{\mathrm {9}}^{+}\), \(\hbox {C}_{\mathrm {7}}\hbox {H}_{\mathrm {7}}^{+}\) and \(\hbox {C}_{\mathrm {6}}\hbox {H}_{\mathrm {6}}^{+}\) were determined to be 8.45, 11.08, 11.47 and 11.17 eV, respectively, with photoionization efficiency spectra (PIES). Three dissociation pathways of parent ions are investigated by experimental photoionization and the quantum-chemical calculations. The fragment ions \(\hbox {C}_{\mathrm {7}}\hbox {H}_{\mathrm {7}}^{\mathrm {+}}\) derived from parent ions involved hydrogen atom transfer rather than direct dissociation. Particularly, detailed mechanisms of dissociation \(\hbox {C}_{\mathrm {6}}\hbox {H}_{\mathrm {6}}^{+}\) are presented for the first time in this work. In addition, the geometries of the intermediates (INTs), transition states (TSs) and products have been performed at B3LYP/6-311 \(+ \,+\) G (d, p) level. The mechanisms of dissociative photoionization of o-xylene and the INTs and TSs involved are discussed in detail.

Graphic Abstract

中文翻译：

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邻二甲苯的VUV光电离和离解光电离：实验和理论见解

摘要

已经使用同步加速器辐射真空紫外光研究了邻二甲苯的光电离和离解光电离，其光子能量在8.0-13.0 eV的范围内。邻二甲苯的电离能和主要碎片离子的出现能\（\ hbox {C} _ {\ mathrm {8}} \ hbox {H} _ {\ mathrm {9}} ^ {+} \），\（\ hbox {C} _ {\ mathrm {7}} \ hbox {H} _ {\ mathrm {7}} ^ {+} \）和\（\ hbox {C} _ {\ mathrm {6} } \ hbox {H} _ {\ mathrm {6}} ^ {+} \）通过光电离效率谱（PIES）分别确定为8.45、11.08、11.47和11.17 eV。通过实验光电离和量子化学计算研究了母离子的三种解离途径。碎片离子从母离子衍生的\（\ hbox {C} _ {\ mathrm {7}} \ hbox {H} _ {\ mathrm {7}} ^ {\ mathrm {+}} \）涉及氢原子转移而不是直接解离。特别是，在本工作中首次提出了详细的解离机制\（\ hbox {C} _ {\ mathrm {6}} \ hbox {H} _ {\ mathrm {6}} ^ {+} \）。此外，中间体（INTs），过渡态（TSs）和产物的几何形状已在B3LYP / 6-311 \（+ ,, + \） G（d，p）级别进行。详细讨论了邻二甲苯的离解光电离机理以及涉及的INT和TS。

图形摘要