Calculation of X-Ray Intensities from Electron Probe Specimens

Abstract

Complete calibration curves may be prepared for electron probe specimens of any matrix composition without the aid of known calibration standards. When there is no fluorescent excitation of the desired element by matrix components, the equation for relative x‐ray intensity is simply I_A/I₁₀₀ = F_AW_A/F_A100, where I_A and I₁₀₀ are the intensities from weight fraction W_A and from 100% of the element, respectively; F_A and F_A100 are values of an ``intensity variable'' at W_A and 100% of the desired element. Values of F for all elements from Ti to Au (and probably from Al to Ti as well) for any takeoff angle ψ, and for any matrix composition, can be obtained from a single intensity‐variable curve that will, of course, be valid for any electron probe instrument operated in the 25–30 kev range. When there is fluorescent excitation of the desired element A by characteristic radiation from matrix element B, the equation is the same except for a fluorescent correction term K_F, which is evaluated from tabulated values of absorption coefficients and excitation efficiencies. Then I_A/I₁₀₀ = F_AW_A(1+K_F)/F_A100. For the NRL electron probe operated in the 25–30 kev range, x‐ray intensities calculated from these equations agreed with measured values to within 5% of the amount present even when very strong fluorescence by matrix elements occurred.