## Comparison between the experimentally measured Xe@C_{60} photoionization cross section (square with error bar) [3] and theoretical calculations using spherical potential 1 (dash, magenta) and fitted jellium potential 2 (solid, green)

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**Figure 3.** Comparison between the experimentally measured Xe@C_{60} photoionization cross section (square with error bar) [3] and theoretical calculations using spherical potential 1 (dash, magenta) and fitted jellium potential 2 (solid, green). Theoretical results are divided by 6.5 to match the measurement. The reduced experimental cross section of Xe [22] is also presented for comparison; see text.

**Abstract**

Confining resonances in the photoionization of endohedral atoms are a topic of major research interest. The C_{60} fullerene cage has been commonly modelled as a spherical attractive cavity and more recently with a newly proposed jellium model (Verkhovtsev *et al* 2012 *J. Phys. B: At. Mol. Opt. Phys.* **45** 215101). In this work, the bound wavefunctions are determined by solving the relativistic multiconfiguration Dirac–Fock equations. The photoionization cross sections of Xe and Xe@C_{60} have been calculated using the relativistic *R*-matrix method for both a spherical attractive cavity and the newly proposed jellium potential. Comparison between the present calculations and other experimental and theoretical results demonstrate that configuration interaction has an important effect. The resonance resulting from confinement by the fullerene cage compares well with the experimental measurements.