Photoionization of Onion-type atoms

The photoionization of a two-shell ("onion") endohedral A@C$_{\rm N1}$@C$_{\rm N2}$ is considered. The effect of the fullerenes shells upon photoelectron from atom A is taken into account substituting the action of the fullerene by two zero-thickness "bubble potentials". The fullerenes shells polarization is included assuming that the radius of the outer shell $R_2$ is much bigger than the inner $R_1$ and both much exceed the atomic radius $r$. The interaction between shells C$_{\rm N1}$ and C$_{\rm N2}$ is taken into account in the Random Phase Approximation (RPA). The effect of photoelectron scattering by both "bubble potentials" is included in the RPA frame. As concrete examples, two endohedrals Ar@C$_{60}$@C$_{240}$ and Xe@C$_{60}$@C$_{240}$ are considered. We investigate $3p$4 Ar and $5p$ Xe subshells.