Improved universal empirical and theoretical fits for K x-ray production cross sections

The relevance of x-ray production cross sections (XRPCS) and the related ionization cross sections (ISC) in many research areas has been described at length and analyzed in detail [1]. X-ray emission cross sections by ion impact are a relevant input in many areas such as studies of track structure in biological matter. Particle Induced X-ray Emission (PIXE) strongly requires trustworthy databases for XRPCS and/or reliable predictions of inner-shell ionization theories as periodically evaluated in Monte Carlo Geant4 simulations [2].

To check if theories are accurate across the periodic table of elements and a large range of projectile energies, equally comprehensive databases are essential and a universal fit for them is desired.

In the Spring APS Annual Meeting [3], the fits for 6537 K-shell XRPCS induced by protons were marred by significant deviations for several target elements.

Although the mean ratio of all data to the fit was 1.03 their standard deviation was an unacceptable 149%.

After elimination of the data that are higher or lower than 1.0 for each target element by a factor of 5, a much-improved fit for all data is presented here.

Its 34% standard deviation is comparable to the reported uncertainties in the compiled XRPCS. The outliers so chosen are just 0.75 % of all 6537 XRPCS.

[1] J. Miranda and G. Lapicki 2014 ADNDT 100 651.

[2] S. Incerti, P. Barberet, G. Deves, and C Michelet. 2015 NIM.B 358 210.

[3] G. Lapicki, contributed presentation at a Frontiers in Fundamental Physics session of the American Physical Society Meeting, 11-15 March 2022, Chicago, USA.