Electronics Caused By The Atomic Inner-shell Ionization Cross Section Measurements, New Methods And New Results

The experimental and theoretical study of atomic inner-shell ionization cross sections by electron impact, a subject of scientific study for many years, is important both for theory and practical application. On the one hand, these data are of basic importance in attempts to better understand inelastic electron-atom interactions and to test the accuracy of various theoretical calculation, such as plane wave Born approximation (PWBA); binary encounter approximation (BEA); distorted wave Born approximation (DWBA) and so oa On the other hand, cross sections for the removal of atomic inner-shell by electron impact are needed in fields of application including materials analysis by electron-probe microanalysis (EPMA), surface analysis by Auger-electron spectroscopy (AES), and thin film analysis by electron energy-loss spectroscopy (EELS). Furthermore, high precision cross sections are particularly desired in the research of nuclear fusion plasma to diagnose absolute impurity concentrations.Nevertheless, despite more than seven decades development, there is still inadequate experimental and theoretical knowledge of the dependence of the ionization cross sections for different inner-shells on atomic number and electron energy. The main difficulty has been the preparation of thin targets. It is well known that the criteria for thin target condition is △ E/E<< 1, where E and △ E represent the incident energy of electron and the energy loss of the incident electron passing through a thin target, respectively. In low energy region, thin and uniform self-supporting targets are difficult to prepare. For example, if △ E/E = 0.02, for Cu target, the self-supporting thin target doesn't exceed 50 nm for 20keV incidental electron. Except few metal elements such as Au, Cu, Ni etc, self-supporting targets can't be produced for many elements. Moreover, it isn't easy to reserve the self-supporting targets and to keep theirs homogeneity.A new method has been performed in the dissertation. The thin targets with thick substrate, which could be easily prepared by vacuum coating techniques, are used in the experiment. Since electrons reflected from the substrate should induce ionization of the target atom, which will increase the number of counts of characteristic X-ray, correction should be made for this effect. For the correction method we should know the reflection spectra of incident electrons from the substrate, which can be precisely calculated according to the bipartition model of electron transport. So the influence of the substrate can be eliminated. Basing on this method, the author measured some important elements such as Zn, Ge, Se, Y, Sc and V K-shell and Sn, Re and In L-shell cross sections etc, the experimental data are reported for the first time for some of them. The results are in agreement with the empirical formula of Casnati et al for K-shell results.Using the existing data, the author provides a new empirical expression for K-shell ionization cross sections by electron impact. The empirical expression can be used in wider region for atom and electron energy than the other empirical formulas. The predictive results are in good agreement with the existing cross sections data and typically better than ±10%.The author has compiled all the experimental data for L-shell in the appendix of the dissertation. It is helpful for people who work in this field.