Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
J Phys Chem A. 2009 Dec 31;113(52):14923-9. doi: 10.1021/jp9050726.
Dissociative electron attachment to all three isomers of dichlorobenzene has been investigated in the electron energy range from 0 to 2 eV and in the gas temperature range from 391 to 696 K using a crossed electron-molecular beam apparatus with a new temperature-regulated effusive molecular beam source. In the case of the dissociative electron attachment channel Cl(-)/1,2-dichlorobenzene and Cl(-)/1,4-dichlorobenzene, strong enhancement of the negative ion production with the gas temperature at low electron energies has been observed. The low-energy peak increases dramatically when the gas temperature is raised from 391 to 696 K. Activation energies for dissociative electron attachment of (482 +/- 20) meV for 1,2-dichlorobenzene and (59 +/- 20) meV for 1,4-dichlorobenzene have been determined. For the resonance at (0.49 +/- 0.03) eV in 1,2-dichlorobenzene and (0.32 +/- 0.03) eV in 1,4-dichlorobenzene, no dependence of the cross sections on the gas temperature has been observed. In the case of the dissociative electron attachment to Cl(-)/1,3-dichlorobenzene, the cross section does not depend on the temperature in the electron energy range from 0 to 2 eV. Quantum chemical calculations of the reaction energies and of the potential energy curves involved in the dissociation of Cl(-) have been performed, together with an analysis of the thermo dynamical accessibility of the relevant vibrational modes. Possible reasons for the different temperature dependences of the isomers are discussed.
用电子-分子束交叉装置和新的控温扩散分子束源，在电子能量 0-2eV 范围内和气体温度 391-696K 范围内，研究了三种二氯苯异构体的电子离解吸附。对于 Cl(-)/1,2-二氯苯和 Cl(-)/1,4-二氯苯的离解电子吸附通道，在低电子能量时，随着气体温度的升高，负离子的产生有强烈的增强。当气体温度从 391K 升高到 696K 时，低能峰急剧增加。确定了 1,2-二氯苯的离解电子吸附的活化能为（482 +/- 20）meV，1,4-二氯苯的活化能为（59 +/- 20）meV。对于 1,2-二氯苯中的（0.49 +/- 0.03）eV 共振和 1,4-二氯苯中的（0.32 +/- 0.03）eV 共振，截面不随气体温度的变化而变化。对于 Cl(-)/1,3-二氯苯的离解电子吸附，在 0-2eV 的电子能量范围内，截面不随温度而变化。进行了 Cl(-)离解涉及的反应能和势能曲线的量子化学计算，并分析了相关振动模式的热力学可达性。讨论了异构体不同温度依赖性的可能原因。
