The value of the photoionization cross section of hydrogen at energies above 1 keV

[AtsushiTanimoto]

Thank you for maintaining the xraylib code.

We used the xraylib.CSb_Photo_Total function to calculate photoionization cross sections of hydrogen. We then compared the photoionization cross sections obtained from the xraylib code with those of EPDL97 as used in Geant4.

As a result, in the energy band lower than 1 keV, the cross sections obtained from the xraylib code were in good agreement with those of EPDL97. However, in the energy band higher than 1 keV, the cross sections obtained from the xraylib code were smaller than those of EPDL97. Why do these values differ?

Regards,
Atsushi Tanimoto

[tschoonj]

Hi Atsushi,

Apologies for my late response.

I had a look into the discrepancy and all I can say with certainty is that the data reproduced by xraylib is correct in the sense that it matches what is listed in the Kissel dataset from which it is retrieved.

I did notice that the data in the same file for the total photoionization cross section is closer to the Geant4 data, but that data is not used by the xraylib.CSb_Photo_Total function, and instead this function sums up the individual partial phootionization cross sections, as this allows for adjustments (extrapolations) to take into account the set of edge energies in use by xraylib, which differs slightly from those used by Kissel.

Hope this helps!