Dresden 2011 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 6: Precision spectroscopy of atoms and ions II
A 6.8: Vortrag
Montag, 14. März 2011, 18:15–18:30, BAR 205
First measurement of the ionization potential of astatine — •Sebastian Rothe1,2, Andrei N. Andreyev3, Stano Antalic4, Thomas E. Cocolios1, Dimitry V. Fedorov5, Lars Ghys6, Mark Huyse6, Yuri Kudryavtsev6, Jens Lassen7, Bruce A. Marsh1, Dieter Pauwels6, Deyan Radulov6, Sebastian Raeder2, Maxim Seliverstov5,6, A. Marica Sjödin1, Piet Van Duppen6, Martin Venhart8, Klaus Wendt2, and Valentin N. Fedosseev1 — 1CERN, Geneva, Switzerland — 2Institut für Physik, Uni Mainz, Germany — 3University of the West of Scotland, Paisley, UK — 4Comenius University, Bratislava, Slovakia — 5PNPI, Gatchina, Russia — 6IKS, KU Leuven, Belgium — 7TRIUMF, Vancouver, Canada — 8Slovak Academy of Sciences, Bratislava, Slovakia
Since the discovery of element 85 in the year 1940 by D. R. Corson et al., the binding energy of the outer electron of astatine had not been determined. At the on-line isotope separator facility ISOLDE at CERN, Geneva radioactive isotopes of At were produced by impinging 1.4 GeV protons on a uranium carbide target, ionized using the Resonance Ionization Laser Ion Source (RILIS) and detected using alpha decay spectroscopy. In-source laser spectroscopy was performed in order to develop a multi-step ionization scheme for an efficient and highly selective At ion production, as requested by ISOLDE users. Two atomic transitions, previously observed by absorption spectroscopy were confirmed and assigned as first steps of the excitation and ionization scheme. A second laser beam was applied to non-resonantly ionize the excited At atoms. A wavelength scan of the ionizing step was performed to search for the ionization limit. From the observed ionization onset the first ionization potential of At was preliminary determined to be 9.3 eV. Results from these studies at CERN and consecutive measurements at TRIUMF, Canada and IKS, Belgium will be presented.