Efficiency of Production of Characteristic X Radiation from Pure Elements Bombarded by Electrons

Abstract

Equations are presented which give the intensity (photons/electron steradian) of K characteristic x radiation produced by pure elements under electron bombardment at normal incidence. For values of φ (the angle between the x‐ray beam and the specimen surface) between 0° and 90° the equations may be summarized: $$\begin{array}{c}{\nu }_K{\text{=(δω/4π)N}}_K,\\ N_K{\mathrm{=WRf(\chi )NQ̄x}}_K{\mathrm{+N}}_{K_f},\end{array}$$ where v_K is the number of K quanta per incident electron radiated into solid angle δω at takeoff angle φ, W is the fluorescence yield factor, R is a correction for loss of ionization due to electron back scattering, f(χ) is Castaing's absorption correction function, N is the number of atoms per unit volume, Q̄ is an average over electron energy of the cross section for K shell ionization, x_K is the electron path length at which the energy of the electron drops to that necessary for K shell ionization, and N_Kf is the contribution due to secondary K shell ionization by high energy continuous x radiation. It is concluded that the predictions of this theory are in general in good agreement with available experimental data; further, that this theory shows certain advantages over those of Archard (1960) and of Green and Cosslett (1961). Values of f(χ) are calculated and compared with the experimental work of Castaing and the calculations of Archard and Mulvey.