Photoionization cross section of Xe
Figure 1. Photoionization cross section of Xe. Experimental measurements and other theoretical calculations are also presented for comparison: circle  and square  with error bar are experimental data; solid and dash lines are the present calculations in length (solid, blue) and velocity (dash, magenta) gauges, R-matrix results  in length (dash line with open circle, olive) and velocity (dash line with open square, green) gauges, RPAE results of  (solid line with open circle, violet) and  (solid line with open square, red), and TDLDA results  (dot line with star, wine).
Confining resonances in the photoionization of endohedral atoms are a topic of major research interest. The C60 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@C60 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.