Jorge Machado

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.

Physics Letters B, 809 (2020) 135748. 10.1016/j.physletb.2020.135748

In this work, we present K- and L- shell fluorescence yield values of the full isonuclear sequence of Fe ions, using a state-of-the-art multiconfiguration Dirac–Fock approach. These results may be of importance for spectral fitting and plasma modeling, both in laboratory and astrophysical studies, where Fe is an important benchmark element. The K-shell fluorescence yields were found to be very similar up to the removal of 14 electrons.

In this paper, we present a theoretical study of the X-ray fluorescence emission after vacancy of K-shell due to electron impact ionization. In particular, we focus on the angular distributions of the characteristic Kα emission lines following this process. Rh was chosen for the analysis since it is a common element in X-ray tube anodes. In this analysis we also considered some elements along the period-4, i.e., Ni, Cu and Co as case-studies. In doing so, we studied the magnetic sub-level population of the ionized states, which is directly related to the angular distribution of the emission. A relative low angular distribution for the Kα emission of Rh of 0.5% was observed, which makes the assumption of isotropic emission correct for most studies. Moreover, a comparison with the respective angular emission for adjacent elements in the fourth period of the periodic table shows that this isotropy is attributed to a small total angular momentum of the resulting configurations after ionization, as well as to opposite angular distributions of the various transitions, which average to a maximum of 0.7% angular asymmetry in Ni.

Radiation Physics and Chemistry, 194 (2022) 110048. doi:10.1016/j.radphyschem.2022.110048

The simulation of atomic relaxation relies on data libraries with tabulated partial fluorescence yield values of radiative transitions, commonly derived from the Evaluated Atomic Data Library (EADL)....

Zinc K-shell radiative and radiationless transition rates are calculated using the multiconfiguration Dirac–Fock method. Correlation up to the 4p orbital is included in almost all transition rate cal...

Phys. Rev. A 97, 032517 (2018). doi:10.1103/PhysRevA.97.032517

Journal of Analytical Atomic Spectrometry (2020), 35, 2920-2927, doi:10.1039/D0JA00307G