AbsoluteK-Ionization Cross Section of the Nickel Atom under Electron Bombardment at 70 kv

Nickel sheets approximately 5×{}10^-6 cm in thickness were bombarded with 70 kv electrons and the intensity of the resulting Kα radiation was measured by a special air-filled ionization chamber connected to a calibrated quadrant electrometer. Isolation of the Kα line was effected by Ross filters of cobalt and iron, supplemented by additional filters for evaluation of a correction for the continuous background radiation. After due consideration of the effects of electron scattering in the target and all relevant x-ray absorptions, it was concluded from the observed intensities that the cross section of the nickel atom for K ionization by 70 kv electrons is (3.38±{}0.2) ×{} 10^-22 cm². From this result and Williams' equation for electron energy loss it is deduced that the efficiency of production of nickel K-radiation by electrons of 70 kev energy is 0.35 percent.