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The L 2,3 -MM Auger spectra of argon have been created bombarding the sample gas by either 2 keV electrons or 398 eV and 315 eV photons. The 2p photoionization created by 315 eV photons may be accompanied by a simultaneous excitation of another electron to an unoccupied orbital or to the continuum. High-energy electrons and 398 eV photons can ionize the 2s subshell which may lead to the L 1 -L 2,3 [M]-MM[M] satellite Auger transitions. Semiempirical kinetic energies of the L 2,3 [M]-MM[M] satellite Auger transitions have been estimated with the aid of MCDF calculations, the 2p shake-up spectrum, the L 1 -L 2,3 M Coster-Kronig spectrum and the final-state binding energies from optical data. Intensities of the transitions have also been calculated by using a MCDF code. A comparison of the semi-empirical and observed energies with the calculated and observed intensities has allowed us to assign a manifold of the satellite peaks in the measured spectrum. We have also investigated the changes in intensity distribution of satellites in passing from cascade satellites to those created via shake-off processes accompanying photoionization.

Auger decay of the inner-shell doubly excited 4d 9 5p 5 nlnЈlЈ states in Xe is studied by experiment and theory. The ''single-participator,'' ''double-participator,'' and ''spectator'' decay channels of the resonance states are calculated in a two-step approximation. The results are used to explain the observed resonance enhancement of the Xe 5p 4 nl photoelectron satellite intensities in the photon energy range 73-87 eV. ͓S1050-2947͑99͒51204-3͔PACS number͑s͒: 32.80. Hd, 32.80.Fb The tunable photon energy of synchrotron radiation offers an effective tool to study various photon-energy-dependent phenomena in atomic and molecular photoionization. For instance, at certain photon energies above a core ionization threshold a core electron and an additional outer-shell electron can both be resonantly excited to unoccupied Rydberg orbitals; i.e., a neutral doubly excited state is created. Knowledge of ionization through the Auger decay of doubly excited states is a key to the understanding of the interactions within a system of many electrons. In this work the interactions of the inner-shell doubly excited 4d 9 5p 5 nlnЈlЈ states of Xe with Xe ϩ states are studied.Analogously to singly excited states ͑e.g., 4d 9 np), doubly excited states decay prominently via resonant Auger transitions, where the initially excited electrons may or may not take part in the filling of the holes. In a ''doubleparticipator'' transition one of the excited electrons fills an initial-state hole and the other is ejected as an Auger electron. In the case of 4d 9 5p 5 nlnЈlЈ doubly excited states the ''double-participator'' transitions populate the same 4d or 5 p single-hole final states as created via direct photoionization.In a ''single-participator'' process ͑e.g., 4d 9 5p 5 nlnЈlЈ→5p 4 nl) only one of the excited electrons participates actively while the other remains as a spectator. If both electrons are initially excited to np orbitals ͑e.g., 4d 9 5p 5 6p 2 ) the odd-parity final states are of the type 5p 4 np, where nϭ6 for the pure participator and nу7 for the shake-modified participator transitions. These final states can also be reached in a direct 5p photoionization accompanied by the 5p→np shakeup ͓1͔. If the initial excitation populates states with both excited electrons in ns and/or nd orbitals ͑e.g., 4d 9 5p 5 5d 2 ), the even-parity Auger final states are identical to the 5s correlation satellite states ͑e.g., 5 p 4 5d). A third possibility for the doubly excited states to decay is the pure spectator transition ͑e.g., 4d 9 5p 5 nlnЈlЈ →5p 3 nlnЈlЈ), where both excited electrons remain in their initial orbitals, or only shake during the decay.The double excitation of the two electrons in He has been widely studied since its first observation by Madden and Codling ͓2͔. Resonance enhancement of the valence satellites at Ne 2s 1 2p 5 nlnЈlЈ double-excitation resonances was reported by Becker et al. ͓3͔. Studies of inner-shell doubly excited states have so far been rare, mainly due to the lack of suitable photon sources with high e...

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