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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 Rothe^1,2, 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 Seliverstov^5,6, 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.