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.

Cross sections for double photoionization of the Ne L shell into the 2s2p5 3po and I P" and the 2s02p6 I se states were measured for energies from threshold up to 150 eV. using photon induced fluorescence spectroscopy. Both 2s2p5 channeIs were observed with comparable magnitude in contradienon to a propensity rule based on the Wannier-Peterkop-Rau theory. A comparison of the summed 3po and IP" cross sections with MBPT calculations results in a deviation of 50%.

A survey of the experimental method of photon induced fluorescence spectroscopy applied in the VUV is given. Results obtained at BESSY for photoionization of the Ar 3s-electrons are presented in an exemplary fashion in a comparison with published results obtained by photoelectron spectroscopy. For this comparison resonances close to threshold and the energy dependence in the threshold range have been selected.