Theoretical Fitting of the ArgonKAbsorption Spectrum on a One-Electron Model

The one-electron model was used to analyze the argon $K$ absorption spectrum near the $K$ edge. It was assumed that the absorption spectrum consists of (1) two Lorentzians due to $1s\to 4p$ and $1s\to 5p$ resonant transitions, (2) a modified arctangent to account for the $1s\to \mathrm{np}(n\ge 6)$ and the $1s\to \mathrm{continuum}\mathrm{transitions}$, and (3) a constant background due to the $L$, $M$ ionizations. The transmission spectrum containing adjustable parameters was constructed on the one-electron model and was then smeared by the experimental window function. The values of these parameters were selected to minimize the ${\chi }^2$ value between the observed transmission curve and the smeared-model transmission curve. The criterion showed that the present model fits the observed curve. Pertinent parameters were interpreted in terms of oscillator strengths and the $K$-state width. The oscillator strengths (0.00217 and 0.00066) of the $1s\to 4p$ and $1s\to 5p$ transitions show fair agreement with the theoretical values (0.00166 and 0.00053). The $K$-state width parameter is 0.68 eV, which compares well with the value obtained by several different spectral methods as well as the value obtained from the $K$ fluorescence yield.