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High-resolution Cl 2p Ϫ1 photoelectron ͑PES͒ and Cl 2p Ϫ1 →3p Ϫ2 normal Auger electron spectra ͑AES͒ have been measured using different photon energies. The PES and AES have been fitted simultaneously taking vibrational and electronic lifetime-interference terms into account. Detailed results are presented for the Cl 2p Ϫ1 →3p Ϫ2 normal Auger transitions. The equilibrium distances, vibrational energies, and anharmonicities for the 1 ⌺ ϩ , 1 ⌬, and 3 ⌺ Ϫ final states are derived from the intensity distribution of the vibrational substates. The relative intensities for the different Cl 2p Ϫ1 →3p Ϫ2 normal Auger transitions are also given. In addition to the Cl 2p Ϫ1 →3p Ϫ2 transitions, some fine structures are observed that show a photon energy dependence. These structures are assigned to decays of doubly excited or shake-up/off states.

Fully relativistic, self-consistent field calculations, based on the Dirac-Coulomb-Gaunt Hamiltonian, were performed on the ground state of HBr, the Br 3d -ionized HBr ϩ , and the 4p(,) Ϫ2 states of HBr 2ϩ . Correlation in the ground and valence-excited states and partially in the Br 3d ionized states was described using a configuration-interaction ͑CI͒ method. Calculated ionization energies and bond lengths were found to be in good agreement with recent experimental results. The distortion in the vibrational bands of the 3d Ϫ1 →4p Ϫ2 Auger transitions due to lifetime vibrational interference was verified through ab initio calculations. Bands due to the transitions to bound and continuum vibrational states of the same electronic state were reproduced by calculations and compared with experimentally determined profiles. The nonadiabatic effects in the spin-orbit-induced avoided level crossing were investigated using adiabatic and diabatic electronic basis sets.

In this paper, high resolution Br 3d photoelectron spectra of HBr are presented. Experimental lifetime widths of the ligand-field-split Br 3d components have been derived, and compared with theoretical predictions based on the one-centre approximation accounting for relativistic effects. The dependence of the theoretical decay widths on the kinetic energy for the Auger electron and the correlation in the final states of the Auger decay has also been investigated.

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...