Experimental evidence of confinement resonances in the photoionisation of the endohedral Xe@C$_{60}^{+}$

A recent communication [1] presented experimental evidence of confinement resonances associated with the photoabsorption by a noble gas atom in a C$_{60}$ cage. The giant 4d resonance in the photoionization of Xe is predicted to be modulated into four components when the Xe atom is confined within C$_{60}$ due to multi-path interference of photoelectron waves caused by reflection from the C$_{60}$ cage. The measurements were performed in the photon energy range 60 - 150 eV by merging a beam of synchrotron radiation with a mass/charge selected ion beam current at a fraction of a picoampere, of the endohedral. The phenomenon was observed in the cross section for double photoionization of Xe@C$_{60}^+$ accompanied by fragmentation of two carbon atoms, yielding Xe@C$_{58}^{3+}$ product ions. This research was supported by the Division of Chemical Sciences, Geosciences and Biosciences of the U.S. Department of Energy, the Deutsche Forschungsgemenischaft, Germany and CONACYT-82521, M\'{e}xico.[1] A.L.D. Kilcoyne et al., Phys. Rev. Lett. 105, 213001 (2010)