Near-threshold absolute M -shell x-ray production cross sections of Au and Bi by electron impact

Abstract

Absolute M -shell x-ray production cross sections have been measured and calculated for Au and Bi for electron incident energies from close to the ionization threshold up to 38 keV. The experimental cross sections were deduced from Mα x-ray intensities emitted from ultrathin Au and Bi samples deposited on self-supporting C films. The measurements were performed on an electron microprobe using several wavelength-dispersive spectrometers. The x-ray production cross sections were also evaluated theoretically using ionization cross sections calculated from the plane-wave and the distorted-wave Born approximations. Experimental results are compared with the calculated cross sections and also with the results of two analytical formulas widely used in many applications. Good agreement is found between the measured cross sections and the predictions from the distorted-wave Born approximation, which indicates that this approximation is suited for the calculation of M -shell ionization cross sections of heavy elements. © 2008 The American Physical Society.