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Cross sections for photon-induced production of Ne+ in the 2p4(3P)3p 2P, 4P, 2D, 2p4(1D)3s 2D and 2s2p6 2S states have been measured for energies between 52 eV and 55.5 eV. Linearly polarized undulator radiation with a bandwidth of 18 meV and 4.5 meV was used. The applied method of photon-induced fluorescence spectroscopy allows the measurement of the alignment A20 of the excited states with all fine structure components being resolved. Autoionization from doubly excited Rydberg states was observed as a dominating population mechanism, except for the 2p4(3P)3p 2PJ and the 2s2p6 2S1/2 states. These states are also populated directly, showing interference profiles in their cross section energy dependence. The remarkly direct population of the 2p4(3P)3p 2PJ states and the excitation of the 2p4(3P)3p 2P3/2,1/2 ns,nd Rydberg series can qualitatively be related to the 2p53p admixture of the Ne ground state. The measured alignment values allow an analysis of the photoelectron partial waves with respect to the dominating jel values. So far, no theoretical analysis has been carried out for comparison.

Photodissociation processes of O2 at exciting-photon energies between 17 and 19 eV were investigated through dispersed fluorescence excitation spectra in the VUV spectral range, by measuring the intensities of fluorescence lines emitted by neutral excited dissociation fragments between 90 and 105 nm as a function of the exciting-photon energy. The dissociation processes were found to be strongly influenced by predissociation of molecular Rydberg states converging to the O2+ b 4Σg− state, whereas direct dissociation processes resulting from repulsive potentials in the Franck–Condon region were found to be weak. The measured fluorescence excitation functions as a measure for O2 photodissociation were compared with photoionization and ion pair formation cross sections and it was found that the fluorescence excitation functions show similarities to the ion pair formation cross sections.

The alignment of the 5p4 6p levels after the decay of the Xe I 4d9 5/2 6p(J = 1) resonance was investigated experimentally and theoretically. The angular distribution of the visible fluorescence radiation was used to measure the alignment. To calculate the measured quantities the multi-step model was applied, taking account of the relativistic effects within the Pauli-Fock approximation. The influence of the cascade effects on the population of the 5p4 6p levels was estimated.

Ionisation and excitation of atomic oxygen in collisions with protons and electrons were studied experimentally in the intermediate velocity range applying the method of fluorescence spectroscopy. Absolute emission cross-sections for 2s-electron ionisation, excited ion production and excitation of atomic oxygen are presented and for electron impact compared to available data. For proton impact no emission cross-sections have been published so far.

) satellite states have been determinedexperimentally by photon-induced fluorescence spectroscopy. Comparison of the experimental results withtheoretical predictions using multiconfiguration-interaction wavefunctions employing the ab initio R-matrixtechnique are made. Suitable harmony is seen only in the case of cross section ratios for 2s

The first evaluation of a high resolution threshold energy scan of the Ne 2s-electron partial photoionization cross section is presented, obtained from photon induced fluorescence spectroscopy. Strong resonance enhancement is observed, which is related with absorption resonances registered simultaneously.

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.

The de-excitation cross sections of H atoms colliding with molecular hydrogen were determined in the velocity range of 2-. At a mean velocity of the de-excitation cross sections are , and . The velocity dependence of the de-excitation cross sections observed in the experiment agrees with the quadrupole-H dipole interaction and with the quantum character of the molecular rotation.

The angular asymmetry parameter of the photon-induced fluorescence radiation of 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 parameter becomes less structured with increasing total angular momentum J of the photoion. The measurements can be interpreted by a partial-wave analysis of the photofragmentation products. For the population of the ion state only photoelectrons are emitted on all resonances. For the population of the and the ion states the emission of the parity-unfavoured photoelectrons dominates.