Two-electron photoionization of endohedral atoms

Abstract

Using $He@C_{60}$ 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 $% C_{60}$ shell, which "dies out" at relatively high $ε$ values, of about 2$÷$3 two-electron ionization potentials. The results were presented for ratios $R_{C_{60}}(ω,ε)\equiv dσ^{++}(ω,ε)/dσ^{a++}(ω,ε)$, where $dσ^{a++}(ω,ε)/dε$ is the two-electron differential photoionization cross section. We have calculated the ratio $R_{i,ful}= σ_{i} ^{++}(ω)/σ_{i}^{a++}(ω)$, that accounts for reflection of both photoelectrons by the $C_{60}$ 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.