Study of cross-sections for the K-shell ionization of atoms by electron and positron impact

In this paper, the K-shell ionization cross-sections of some atoms by elect ron impact in the energy region less than several ten keV recently measured by our group and by other groups have been compared with the theoretical r esults of plane-wave Born approximation (PWBA) with Coulomb, relativistic. and exchange corrections as well as the Luo and Joy's theory. These experim ental data have also been compared with Casnati et al.'s empirical formula and Deutsch-Margreiter-Mark (DMM) semi-empirical formula, which is modified by us based upon the most recently precisely measured K-shell ionization c ross-sections of Cr, Ni, Cu elements of Llovet et al. Moreover. the experim ental K-shell ionization cross-section ratios of electron and positron impa ct have been re-analyzed using the PWBA with Coulomb, relativistic, and exc hange corrections. It is found that for most of the elements analyzed in th is paper the experimental data are in good or acceptable agreement with the PWBA theoretical results and Luo and Joy's theory and that our modified DM M semi-empirical formula can also provide a good or better description to t he experimental data of K-shell ionization cross-section by electron impact . (C) 2001 Elsevier Science B.V. All rights reserved.