Primary and Secondary Photoelectron Yields Induced by Soft X Rays

A retarding-grid system was developed and used to measure the yields of primary and secondary electrons, Yp and Ys, generated by monochromatic soft x rays. The x-ray source produced fluorescent lines at eight energies ranging from 1.26 to 5.41 keV. Emission was studied from "standard" surfaces of aluminum foil, anodized aluminum, gold, silver, titanium, silicon, glass, Saran, Mylar and carbon. At x-ray energies between the absorption edges of a material, the yields have powerlaw dependences on x-ray energy. The primary yields can be represented by Yp=GμxΣfiSi where G is a constant for a material, μx is the x-ray absorption cross section and ΣfiSi is a summation of the weighted CSDA ranges for the photo- and Auger electrons produced in the material. Values for G ranged from 0.11 to 0.18. At 1.26 keV, the secondary electron coefficient, Ys/Yp, ranged from about 6 for glass and Al2O3 down to 1.8 for silicon and 1.2 for Mylar; at higher photon energies the values of Ys/Yp gradually decreased by factors of 2.5 to 3.5.