电子碰撞Ne和类Ne离子电离的三重微分截面理论研究

Theoretical studies of triple differential cross sections for electron impact ionization with neon and neon-like ions

采用扭曲波玻恩近似理论计算了共面对称几何条件下类Ne离子2p轨道电子在不同出射电子能量下的(e,2e)反应三重微分截面,出射电子能量分别为3,5,7.5,10,15,20,30和50 eV.计算结果表明,随着出射电子能量的增大和核电荷数Z的增大,三重微分截面的幅度逐渐减小.除Ne以外,对其他离子,在出射电子角度为150?附近出现了一个新的结构,对比不同出射电子能量时的(e,2e)反应三重微分截面,发现这个结构的幅度随着出射电子的能量先增大后减小,文中用一种两次两体碰撞过程对这些现象进行了解释.

Electron impact single ionization of atom or molecule, the so-called（e, 2e） reaction, is one of the basic collision processes between electron and atom or molecule. The triple differential cross section（TDCS） of the collision process can provide important data for gas discharge, celestial bodies, and electron-target interaction.A large number of experimental and theoretical studies of（e, 2e） reactions on atom targets have been carried out under different geometric conditions, such as coplanar symmetric geometry, coplanar asymmetric geometry, non-coplanar symmetric geometry, etc. However, few experimental researches of（e, 2e） reaction on ion target have been reported due to the low target source density. The difference in TDCS between atomic target and ionic target can provide more information about the（e, 2e） reaction. Thus the relevant researches on ionic targets are of significance.In this paper, adopting distorted-wave Born approximation（DWBA）, the TDCSs of 2p orbital for Ne and neon-like ions are calculated at different outgoing electron energies（3, 5, 7.5, 10, 15, 20, 30, and 50 eV） under the condition of coplanar symmetric geometry. The results indicate that the TDCSs decrease with the increase of outgoing electron energy and nuclear charge number Z. Except Ne, the TDCSs of other ions present a new structure at an outgoing electron angle of about 150？. The intensity of the new structure increases with the increase of the outgoing electron energy in a region of 10–20 eV, while it decreases with the increase of the outgoing electron energy in a region of 20–50 eV.We propose a kind of double-binary collision process to rationalize the new structure. The incident electron ionizes the target atom and the following two outgoing electrons exit in the directions symmetric with respect to the incident electron direction. Then these two outgoing electrons are elastically scattered by the target ions and emitted in the backward directions. In order to confirm this explanation, we compare our calculation results with the previously reported experimental and theoretical results of elastic scattering between electron and Ne. Previous research results show that the elastic scattering cross section has a large intensity at a scattering angle of ~150？, and it reaches the largest intensity at an outgoing electron energy of 20 eV. These structural features are consistent with our calculated results, implying that our proposed process is reasonable.