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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Understanding the complex dissociation dynamics of energy selected dichloroethylene ions: Neutral isomerization energies and heats of formation by imaging photoelectron-photoion coincidence
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Understanding the complex dissociation dynamics of energy selected dichloroethylene ions: Neutral isomerization energies and heats of formation by imaging photoelectron-photoion coincidence

机译：了解能量选择的二氯乙烯离子的复杂解离动力学：通过对光电子-光子重合进行成像，中性异构化能和形成热

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摘要

The dissociative photoionization of 1,1-C2H2Cl 2, (E)-1,2-C2H2Cl2, and (Z)-1,2-C2H2Cl2 has been investigated at high energy and mass resolution using the imaging photoelectron photoion coincidence instrument at the Swiss Light Source. The asymmetric Cl-atom loss ion time-of-flight distributions were fitted to obtain the dissociation rates in the 103 s-1 < k < 107 s-1 range as a function of the ion internal energy. The results, supported by ab initio calculations, show that all three ions dissociate to the same C 2υ symmetry ClC=CH2+ product ion. The 0 K onset energies thus establish the relative heats of formation of the neutral isomers, that is, the isomerization energies. The experimental rate constants, k(E), as well as ab initio calculations indicate an early isomerization transition state and no overall reverse barrier to dissociation. The major high energy channels are the parallel HCl loss and the sequential ClC=CH 2+ → HCCH+ + Cl process, the latter in competition with a ClC=CH2+ → ClCCH+ + H reaction. A parallel C2H2Cl2+ → C2HCl2+ + H channel also weakly asserts itself. The 0 K onset energy for the sequential Cl loss reaction suggests no barrier to the production of the most stable acetylene ion product; thus the sequential Cl-atom loss is preceded by a ClC=CH2+ → HC(Cl)CH+ reorganization step with a barrier lower than that of the second Cl-atom loss. The breakdown diagram corresponding to this sequential dissociation reveals the internal energy distribution of the first C 2H2Cl+ daughter ion, which is determined by the kinetic energy release in the first, Cl loss reaction at high excess energies. At low kinetic energy release, this distribution corresponds to the predicted two translational degrees of freedom, whereas at higher energies, the excess energy partitioning is characteristic of only one translational degree of freedom. New ΔfH°298K of 3.7, 2.5, and 0.2 ± 1.75 kJ mol-1 are proposed for 1,1-C2H 2Cl2, (E)-1,2-C2H2Cl2, and (Z)-1,2-C2H2Cl2, respectively, and the proton affinity of ClCCH is found to be 708.6 ± 2.5 kJ mol-1.
机译：在瑞士使用成像光电子光子重合仪器，在高能量和高质量分辨率下研究了1,1-C2H2Cl 2（（E）-1,2-C2H2Cl2和（Z）-1,2-C2H2Cl2）的解离光电离光源。拟合不对称的Cl原子损失离子飞行时间分布，以得到103 s-1

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