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.

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The angular asymmetry parameter β fl of the photon-induced fluorescence radiation of Ar + (4p-4s) fine-structure resolved satellite lines was measured from threshold up to 38.4 eV. It is well known that the cross sections of these valence shell satellites are dominated by the decay of aligned doubly excited states leading to an extremely complicated energy dependence. In contrast, we observe that the β fl parameter becomes less structured with increasing total angular momentum J of the photoion. The β fl measurements can be interpreted by a partialwave analysis of the photofragmentation products. For the population of the 4p 2 F 7/2 ion state only d 5/2 photoelectrons are emitted on all resonances. For the population of the 4p 2 D 5/2 and the 4p 4 P 5/2 ion states the emission of the parity-unfavoured d 5/2 photoelectrons dominates.

The absolute cross sections for the 3s-photoionization and the 3p-photoionization of the Ar atom and the Ar-like ions K+ and Ca2+ are calculated. The calculation is performed within the configuration-interaction technique using the Pauli-Fock atomic orbitals. The simultaneous analysis of the calculated and measured total and partial cross sections yields the interpretation of the prominent resonances observed in a recent experiment on Ar above the 3s-threshold.

Results of scanning-tunneling-microscopy (STM) and molecular-dynamics (MD) annealing studies based on quantum-mechanically derived interatomic forces using a semiempirical density-functional approach are combined for analyzing diamond surface structures. Experimentally obtained STM images of diamond (100) and (111)faces on polycrystalline films reveal (1 X 1),(&3 X &3) R 30', and possible (2 X 1) structures. The (100) faces show stable (2 X 1) reconstruction with dimer formation. Surface structures with and without adsorbed hydrogen are determined and their stability is obtained by MD simulated annealing techniques. The bulklike and (&3X&3) 830 structures, as they are observed on grown (111) facets, are attributed to the two diff'erent single atomic (111)layers, which support growth mechanisms, in which the two alternating single atomic layers grow in turn and not simultaneously. The equilibrium surface modifications which have been realized are electronically characterized by investigating the local electronic density of states at selected surface atoms. This information is compared and related to the features seen in the STM images.