Time-dependent close-coupling calculations of the double photoionization of He@C60

The double photoionization of a He atom enclosed in a C-60 molecule, He@C-60 was investigated using the time-dependent close-coupling method with the C-60 molecule represented by a spherical shell potential and the He atom treated nonperturbatively. Comparisons are made with the double photoionization of a bare He atom. The ratio of the total double photoionization cross section of He@C-60 to that of a bare He atom is found to exhibit oscillations due to reflection of a slow electron. This is confirmed by calculations of the single energy differential cross section that peaks at unequal energy sharing when one of the ejected electrons has an energy comparable to the C-60 well depth. Triple differential cross sections are found to be shifted in magnitude, but unchanged in shape from the bare He atom.