A Theoretical Study On The Shield Effect Of The Residual Electron In BBK Model

This thesis presents a systematic and complete theoretical study on the electron impact ionization processes, which consists of electron-atom, by using the BBK method. The shield effect of the residual electron of the BBK model in coplanar and non-coplanar doubly-symmetric geometry is discussed and the applicable geometries of BBK model are expanded. This thesis consists of six chapters.In chapter 1, the connection of energy and momentum, the triple differential cross section and geometries of (e, 2e) reaction are introduce.In chapter 2, we presents a brief overview of the preview research work about the (e, 2e) impact ionization process by using the BBK model. Then the BBK method is introduced detailedly.In chapter 3, we apply the BBK model to the calculation of TDCS for electron impact ionization of helium in the coplanar asymmetric geometry at the Low-energy and high-energy after the shield effect of the residual electron is considered. The influences of these effects on the triple differential cross sections are analyzed.In chapter 4, the triple differential cross section for electron impact ionization of helium in the special geometry of coplanar high incident energies large energy loss and close to minimum momentum transfer and the momentum transfer dependence of the cross section are calculated by use of the BBK and modified BBK model after the shield effect of the residual electron is considered. It is found that both BBK and modified BBK models are in good agreement with the experimental results. The applicable geometries of BBK model are expanded. Then, the influences of the effective shield of residual electron on the triple differential cross sections and the physical nature of these effects are discussed in detail.In chapter 5, the BBK model for electron impact ionization of helium in non-coplanar geometry is analyzed and discussed. It is found that DS3C model is better than 3C model. The effective shield of residual electron in the final state of He + is further modified for (e, 2e) processes. Three different modifications have been proposed in non-coplanar geometry. These influences of the modified Sommerfeld parameters on the triple differential cross sections are discussed and the physical nature of these effects is also considered.In chapter 6, through the theoretical calculation results, we obtain the conclusions.