Why Do UV Photoabsorption Cross Sections Show a Kink at 10-100 Angstrom?

[vrinda mukund]

If we look into the UV photoabsorption cross sections of different gases, a kink in the cross section is seen at wavelength between 10-100 Angstrom. Can some one explain why this happens ?

 

[mfb]

This typically means the energy is sufficient for some ionization process for wavelengths smaller than the kink location.
You get more of th se steps for higher energies when more ionization processes become possible. Here is an example .