A theoretical and experimental study of the behaviour of the correlation satellites arising during 5s photoionization of xenon is presented. Many-body perturbation theory and configuration-interaction techniques have been applied to calculate the wavefunctions of the Xe II ionic states. An expression for the angular distribution parameter of the photoelectrons taking into account final-ionic-state configuration interaction is derived. Photoionization cross sections and angular distribution parameters were calculated for the 5s main line and the majority of the satellite lines and compared with our high-resolution measurements and earlier lower resolution measurements.The differences in the angular distribution parameter dependence on the photon energy for the 5s main line and satellites were analysed in terms of their origin. The most important mechanisms are: interference of several photoionization channels characterizing different orbital momenta of the photoelectron, the mixture of terms with different total orbital momenta in the final ionic state, and the dependence of the photoelectron wavefunctions on the total momentum of the photoelectrons.

The Kr 4s-electron photoionization cross section as a function of the excitingphoton energy in the range between 30 eV and 90 eV was calculated using the configuration interaction (CI) technique in intermediate coupling. In the calculations the 4p spin-orbital interaction and corrections due to higher orders of perturbation theory (the so-called Coulomb interaction correlational decrease) were considered. Energies of Kr n states were calculated and agree with spectroscopic data within less than 10 meV. For some of the Kr 11 states new assignments were suggested on the basis of the largest component among the calculated CI wavefunctions.

Absolute cross sections for the transitions of the Kr atom into the 4s land 4p4nl states of the Kr + ion were measured in the 4s-electron threshold region by photon-induced fluorescence spectroscopy (PIFS). The cross sections for the transitions of the Kr atom into the 4sland 4p4nl states were also calculated, as weIl as the 4p4nln'I' doubly excited states, in the frame of LS-coupling many-body technique. The cross sections of the doubly-excited atomic states were used to illustrate the pronounced contributions of the latter to the photoionization process, evident from the measurements. The comparison of theory and experiment led to conclusions about the origin of the main features observed in the experiment.

Photon-induced fluorescence spectroscopy was applied for the first time to investigate the anisotropy of VUV radiation emitted from Kr II satellite states with total angular momentum J 3 2 after the photoionization of the Kr atom by linearly polarized synchrotron radiation near the 4s threshold. The measurements showed that the sign of the alignment parameter is practically independent of the exciting-photon energy for the ionic state with J = 5 2 , whereas for the states with J = 3 2 the alignment parameter changes sign with varying energy. Simple formulae connecting the angular distribution parameter and the alignment parameter with the kinematics of our experiment and with quantities describing the dynamics of the photoionization were derived in closed form. Partial and total cross sections for the photoionization of 4p, 4s and several satellite levels were calculated taking into account many-electron correlations and doubly-excited states. For the satellite states with J 3 2 the dependence of the angular distribution parameter on the exciting-photon energy was calculated. Good overall agreement between theory and experiment was obtained.

The energy dependence of the alignment parameter A20 for the Kr II 4p45p(E 1J1) states following excitation in the Raman regime with the exciting-photon energy passing through the Kr I 3dJ̄9npj̄ resonances was investigated theoretically and experimentally. Interference between the resonance and direct photoionization channels explains the dependence of A20 on the excitation energy. Experimentally, A20 was determined after the analysis of 5p–5s fluorescence decay of the 4p45p(E 1J1) states excited with monochromatized synchrotron radiation. The band pass of the synchrotron radiation was set to 10 meV which is smaller than the natural width of the 3d9np resonances (∼83 meV). Additionally, a strong energy dependence was predicted for the orientation parameter O10 as well as for the angular distribution parameter of photoelectrons, βe, for several 4p45p(E 1J1) ionic states.

The photoionization cross sections for the production of the Kr 11 4s state and Kr IJ satelJite states were studied in the 4s ionization threshold region. The interference of direct photoionization and ionization through the autoionization decay of doubly-excited states was considered. In the calculations of doubly-excited state energies, performed by a configuration interaction technique, the 4p spin-orbit interaction and the (Kr 11 core)-(excited electron) Coulomb interaction were included. The theoretical cross sections are in many cases in good agreement with the measured values. Strong resonant features in the satellite spectra with threshold energies greater than 30 eV are predicted.

Absolute Kr 4s-eJectron photoionization cross sections as a function of the exciting-photon energy were measured by photon-induced fluorescence spectroscopy (PIFS) at improved primary-energy resolution. The cross sections were determined from threshold to 33.5 eV and to 90 eV with primary-photon bandwidths of 25 meV and 50 meV, respectively. The measurements were compared with experimental data and selected theoretical calculations for the direct Kr 4s-eJectron photoionization cross sections.

Cross sections and angular distribution parameters for the single-photon ionization of all electron orbitals of Li2-8 are systematically computed in a broad interval of the photoelectron kinetic energies for the energetically most stable geometry of each cluster. Calculations of the partial photoelectron continuum waves in clusters are carried out by the single center method within the Hartree-Fock approximation. We study photoionization cross sections per one electron and analyze in some details general trends in the photoionization of inner and outer shells with respect to the size and geometry of a cluster. The present differential cross sections computed for Li2 are in a good agreement with the available theoretical data, whereas those computed for Li3-8 clusters can be considered as theoretical predictions.