The Theoretical Research On Electron-impact-induced Ionization-excitation Reaction Of Helium

The (e,2e) reaction is a multi-body problem, which can’t be solved analytically so far. Hence we should take different approximates, such as the Distorted Wave Born Approximation、R-matrix method、CCC theory and so on. We can also solve some simple three-body problems by using the available theory, for example the impact ionization of H and the single ionization of He, which can also be treated as simple three-body problem on the condition that helium ion is in the ground state after ionization. The result indicates that there is a good fit between the theoretical results and the experiments. When the target ion is in the excited state after ionization, it has become four-body problem. As a result, the corresponding experimental measurements cannot be well interpreted so far, since three active electrons (the scattered electron, the ejected electron and the bound electron), besides the residual ion, are involved in the final state.In the reaction of electron-impact-induced ionization-excitation of helium, under distorted wave Born approximation model, the triple differential cross sections(TDCS) have been calculated through two kinds of He atom initial wave functions(one with no correlations, one with radial and angular correlations). And the theoretical results are compared with experimental data. These comparisons demonstrate that the TDCS results of the Silverman wave function which contains both radial and angular correlations are much better both in peak position and the peak value as well. On the other hand, we find that the angular distribution of the ionization-excitation of helium (e,2e) TDCS has not been affected significantly when we chose different wave functions, or we can say these two states give almost the same angular distribution.Meanwhile, in the reaction of high-middle energy electron impact-induced ionization excitation of helium, under the frist Born approximation model, considering the incident electron、the scattered electron and the ejected electron both all three different wave functions such as distorted wave, plane wave and coulomb wave functions, the triple differential cross sections have been calculated and compared with the experimental data. These comparisons demonstrate that using distorted wave function for the three particles give the best fit for the experiments, and the coulomb wave function next. Otherwise the different wave function of ejected electron has a particular effect on TDCS angular distribution.While the Coulomb wave function next. On the other hand, different wave functions for the ejected electron have a particular effect on the TDCS angular distribution.In chapter one, we mainly introduce the basic principle, current research status and the significance of research of the (e,2e) reaction, especially focusing on the (e,2e) reaction in which the ion is in the excited state after ionization.In chapter two, we use the DWBA method to study the effect of different initial wave functions of He atom on the TDCS of the ionization-excitation of helium, by adopting two different form of He atom initial wave functions in the calculation.In chapter three, we study the effect of three wave functions (plane wave, Coulomb wave and distorted wave) for the incident electron, the scattered electron and the ejected electron on the ionization-excitation of helium TDCS, respectively.In summary, we have used different wave functions to calculate the TDCS. Different effects on TDCS for different wave functions have been analyzed. This paper provides theoretical bases for researchers through theoretical exploration.