The Beam-Foil X-Ray Spectra of Highly Ionized Neon-Like Rhodium, Lanthanum and Gold.

The x-ray spectra of highly ionized neon-like rhodium, lanthanum and gold are observed by accelerating these ions to relativistic velocities and then passing them through thin target foils. Transition energies measured are compared with theoretical multi-configuration Dirac -Fock calculations. Good agreement is observed for most of the transition energies measured at the level of the experimental accuracy, (lambda/Delta lambda~2000), although consistent variations along the isoelectronic sequence on the neon -like transitions to the ground state having an initial state with a 2s hole are observed. This result indicates the inadequate theoretical treatment of the multielectron quantum electrodynamic self energy contributions to these atomic energy level states.