关键词: DS3C模型/
垂直入射/
屏蔽效应/
碰撞机理
English Abstract
A theoretical study on collision mechanisms for low energy electron impact ionization of helium in the perpendicular geometry
Yang Huan1,2,Zhang Sui-Meng2,
Xing Ling-Ling2,3,
Wu Xing-Ju2,
Zhao Min-Fu1,2
1.The Department of Experiment and Practical Training Management, West Anhui University, Liu'an 237012, China;
2.Research Center of Atmos and Molecules and Optical Applications, West Anhui University, Liu'an 237012, China;
3.School of Electrical and Optoelectronic Engineering, West Anhui University, Liu'an 237012, China
Fund Project:Project supported by the Key Projects of Anhui Provincial Department of Education, China (Grant No. KJ2016A749), the Anhui Provincial Natural Science Foundation, China (Grant No. 1408085QA13), the Foundation for Key Research Program of Education Department of Anhui Province, China (Grant No. KJ2012A275), and the Foundation for Key Research Program of Education Department of Anhui Province, China (Grant No. KJ2013A260).Received Date:27 October 2016
Accepted Date:07 January 2017
Published Online:05 April 2017
Abstract:Under the condition of ten different incident energies ranging from 3 eV to 80 eV above the ionization potential of helium and the outgoing electrons having equal energies, by making use of 3C model and modified 3C model, the triple differential cross sections of electron-impact single ionization of the ground state of helium in the perpendicular geometry are calculated. The result is compared with corresponding experimental result to systematically investigate the influences of various screening effects on the triple differential cross sections for helium. The collision mechanisms of the triple differential cross sections are explored. The result shows that the effects of dynamic screening in the final state can directly affect the structures of the triple differential cross sections at lower incident energy, which will unavoidably affect the angular distribution and relative amplitude of side peaks at angles =90 and =270. The screening effects of residual electron in the final state of He+ have a similar significant effect on the amplitude of triple differential cross section of helium and angular distributions and relative amplitudes of side peaks at angles =90 and =270. When the incident energy is over 84.6 eV, the screening effect of residual electron in the final state of He+ has a slight effect on the amplitude of triple differential cross section, which can be overlooked. But the effects of dynamic screening in the final state on side peaks at angles =90 and =270 need considering. In addition, by taking advantage of DS3C-Z model, the results of collision mechanism of various peaks at angles =180, =90 and =270 show that the middle peak at angle =180 is produced by a process called triple scattering mechanism and then the side peaks at angles =90 and =270 are produced by a process called double scattering mechanism. Such a collision mechanism has a direct influence on the generation and variation law of triple differential cross sections.
Keywords: DS3C model/
perpendicular geometry/
screening effects/
collision mechanisms
