Dynamics of electron impact ionization of the outer and inner valence (1t2 and 2a1) molecular orbitals of CH4 at intermediate and large ion recoil momentum
Dynamics of electron impact ionization of the outer and inner valence (1t2 and 2a1) molecular orbitals of CH4 at intermediate and large ion recoil momentum
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中、大离子反冲动量下CH4外价和内价（1t2和2a1）分子轨道电子碰撞电离动力学
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
S. Houamer
中科院分区：
文献类型：
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作者：
A. Lahmam;A. Naja;E. S. Casagrande;N. Okumus;C. Cappello;I. Charpentier;S. Houamer
采用共面不对称运动学的（e，2 e）技术测量了甲烷外价1t2和内价2a1轨道电子碰撞电离的三重微分截面。测量在散射电子能量为500 eV，喷射电子能量为12、37和74 eV以及快速出射电子的散射角为6°的情况下进行。该运动学的特征在于目标离子反冲动量范围从中等（0.25 Au）到非常大（3.2 Au）值。计算结果与理论截面使用1CW和BBK模型最近扩展到分子。实验截面表现出非常大的反冲散射，特别是对于内2a1分子轨道，这是理论所不能预测的。实验和理论之间的差异归因于来自离子的非常强的散射，而理论没有正确地解释。这表明需要进一步的理论发展和实验研究，以便正确地模拟分子电离过程。
The triply differential cross section has been measured for electron-impact ionization of the outer valence 1t2 and the inner valence 2a1 orbitals of methane using the (e,2e) technique with coplanar asymmetric kinematics. The measurements are performed at scattered electron energy of 500 eV, ejected electron energy of 12, 37 and 74 eV and for scattering angle of the fast outgoing electron of 6°. This kinematics is characterized by a target ion recoil momentum ranging from moderate (0.25 au) to very large (3.2 au) values. The results are compared with theoretical cross sections calculated using the 1CW and the BBK models recently extended to molecules. The experimental cross sections exhibit a very large recoil scattering, especially for the inner 2a1 molecular orbital, which is not predicted by the theory. The differences between experiment and theory are attributed to the very strong scattering from the ion, not properly accounted for by theory. This indicates the need for further theoretical developments as well as experimental investigations in order to correctly model the process of molecular ionization.