Comparison of K X-Ray Production by Electron and Positron Impact

The K-shell ionization by electron and positron impact has been studied in the case of Ag at 100, 150, 200, 300, and 400 keV. Results show that the ratios of Kα X-ray production cross section by electron impact to that by positron are obviously larger than unity in the region below 200 keV and the impact energy of positron to yield the maximum cross section is about 80 keV higher than that of electron. A new calculation including the effect of distortion of the projectile wave by the atomic Coulomb field is hoped to explain present results.