Abstract.A crossed-beams setup was used to measure cross sections for electron-impact single and double ionization of W 17+ ions. Absolute data and high-resolution scan spectra were obtained at collision energies ranging from threshold up to 1000 eV. Comparison of the experimental results with theoretical calculations for direct ionization suggests substantial contributions of excitation-autoionization processes to electron-impact single ionization of W 17+ .

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We report results from experiments with the quinoline-O 2 complex, which was photodissociated using light near 312 nm. Photodissociation resulted in formation of the lowest excited state of oxygen, O 2 a 1 Δ g , which we detected using resonance enhanced multiphoton ionization and velocity map ion imaging. The O 2 + ion image allowed for a determination of the center-of-mass translational energy distribution, P(E T ), following complex dissociation. We also report results of electronic structure calculations for the quinoline singlet ground state and lowest energy triplet state. From the CCSD/aug-cc-pVDZ//(U)MP2/cc-pVDZ calculations, we determined the lowest energy triplet state to have ππ* electronic character and to be 2.69 eV above the ground state. We also used electronic structure calculations to determine the geometry and binding energy for several quinoline-O 2 complexes. The calculations indicated that the most strongly bound complex has a well depth of about 0.11 eV and places the O 2 moiety above and approximately parallel to the quinoline ring system. By comparing the experimental P(E T ) with the energy for the singlet ground state and the lowest energy triplet state, we concluded that the quinoline product was formed in the lowest energy triplet state. Finally, we found the experimental P(E T ) to be in agreement with a Prior translational energy distribution, which suggests a statistical dissociation for the complex.

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The MAGIX experiment is a versatile system optimized for low-energy nuclear and particle physics measurements. The setup is currently under development and will be installed at the MESA electron accelerator, at the Institute for Nuclear Physics of the University of Mainz. The main detectors of that experiment are a couple of high-precision magnetic spectrometers, each of them equipped with a GEM-based TPC at the focal plane to achieve a momentum resolution and angular resolution at the scattering vertex respectively of ≈ δ P P < 10 − 4 a n d ≈ 1 1 mrad on scattered electron momenta between 1 MeV/c and 105 MeV/c. The limiting factor to achieve those results is the amount and uniformity of the material before the focal plane and even the presence of the TPC field cage can be relevant. Therefore we developed, and hereby introduce, an open field-cage TPC to fulfil those challenging requirements.

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