Time-dependent close-coupling calculations of the double photoionization of He@C$_{60}$

The double photoionization of a helium atom enclosed in a C$_{60}$ molecule, He@C$_{60}$, has been investigated using the time-dependent close-coupling method [1], with the C$_{60}$ molecule represented by a spherical shell potential and the helium atom treated non-perturbatively. Comparisons are made with the double photoionization of a bare helium atom. The ratio of the total double photoionization cross section of He@C$_{60}$ to that of a bare helium atom is found to exhibit oscillations [2] due to the interference between three photoelectron waves: the photoelectron wave emerging directly from the ionized 1s subshell and the photoelectron waves reflected from the inner and outer boundaries of the C$_{60}$ shell. Single energy differential cross sections and triple differential cross sections are calculated. The investigation is extended to examine the double photoionization of a Helium atom enclosed in a positively or negatively charged C$_{60}$ molecule. \\[4pt] [1] M. S. Pindzola {\it et al.}, J. Phys. B {\bf 40}, R39 (2007).\\[0pt] [2] M. Ya. Amusia, E. Z. Liverts and V. B. Mandelzweig, Phys. Rev. A {\bf 74}, 042712 (2006).