Double ionization of rare gases. II. Ion formation by photon impact

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Abstract
Using synchrotron radiation and a new two-grating grazing-incidence monochromator specially designed to remove higher-order components, the relative intensities of double-photoionization transitions have been measured in helium, neon, and argon between 70 and 200 eV by ion spectrometry. Extensive tests of a new ion spectrometer were undertaken to eliminate any charge discrimination for the ions. These new results resolve discrepancies existing between previous experimental data and favor, in general, the earliest results of Carlson for photon energies higher than 100 eV. For helium and neon they are in good qualitative agreement with theoretical calculations that include electron-electron correlations. In particular they agree very well with the many-body perturbation-theory approach of Chang and Poe in the case of neon.