Using He@C60​ as an example, we demonstrate that static potential of the
fullerene core essentially alters the cross section of the two-electron
ionization differential in one-electron energy dσ++(ω)/dϵ. We found that at high photon energy prominent oscillations
appear in it due to reflection of the second, slow electron wave on the C60​ shell, which "dies out" at relatively high ϵ values, of about
2÷3 two-electron ionization potentials. The results were presented for
ratios RC60​​(ω,ϵ)≡dσ++(ω,ϵ)/dσa++(ω,ϵ), where dσa++(ω,ϵ)/dϵ is the two-electron differential
photoionization cross section. We have calculated the ratio Ri,ful​=σi++​(ω)/σia++​(ω), that accounts for
reflection of both photoelectrons by the C60​ shell. We have calculated
also the value of two-electron photoionization cross section σ++(ω) and found that this value is close to that of an isolated He
atom.Comment: 13 pages, 4 figure