Fundamental Parameters Related To Selenium K Alpha And K Beta Emission X-Ray Spectra

We present relativistic ab initio calculations of fundamental parameters for atomic selenium, based on the Multiconfiguration Dirac-Fock method. In detail, fluorescence yields and subshell linewidths, both of K shell, as well as K beta to K alpha intensity ratio are provided, showing overall agreement with previous theoretical calculations and experimental values. Relative intensities were evaluated assuming the same ionization cross-section for the K-shell hole states, leading to a statistical distribution of these initial states. A method for estimating theoretical linewidths of X-ray lines, where the lines are composed by a multiplet of fine-structure levels that are spread in energy, is proposed. This method provides results that are closer to K alpha(1,2) experimental width values than the usual method, although slightly higher discrepancies occur for the K beta(1,3) lines. This indicates some inaccuracies in the calculation of Auger rates that have a higher contribution for partial linewidths of the subshells involved in the K beta(1,3) profile. Apart from this, the calculated value of K beta to K alpha intensity ratio, which is less sensitive to Auger rates issues, is in excellent agreement with recommended values.