Resonance ionization scheme development for europium
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Resonance ionization scheme development for europium K. Chrysalidis1,2 · T. Day Goodacre1,3 · V. N. Fedosseev1 · B. A. Marsh1 · P. Naubereit2 · S. Rothe1 · C. Seiffert1 · T. Kron2 · K. Wendt2
© Springer International Publishing Switzerland 2017
Abstract Odd-parity autoionizing states of europium have been investigated by resonance ionization spectroscopy via two-step, two-resonance excitations. The aim of this work was to establish ionization schemes specifically suited for europium ion beam production using the ISOLDE Resonance Ionization Laser Ion Source (RILIS). 13 new RILIS-compatible ionization schemes are proposed. The scheme development was the first application of the Photo Ionization Spectroscopy Apparatus (PISA) which has recently been integrated into the RILIS setup. Keywords Resonance laser ionization · Laser ion source · RILIS · Europium · Ionization scheme development · Autoionizing states
1 Introduction The Resonance Ionization Laser Ion Source (RILIS) [1–3] at the ISOLDE radioactive beam facility at CERN [4] is the most intensively used ion source, providing > 75 % of the ion beams in 2016. The RILIS is based on the principle of stepwise laser resonance ionization which is an element (and in some cases isotope or isomer) selective process. Europium
This article is part of the Topical Collection on Proceedings of the 10th International Workshop on Application of Lasers and Storage Devices in Atomic Nuclei Research: “Recent Achievements and Future Prospects” (LASER 2016), Pozna´n, Poland, 16–19 May 2016 Edited by Krassimira Marinova, Magdalena Kowalska and Zdzislaw Błaszczak K. Chrysalidis
[email protected] 1
CERN, CH-1211 Geneva 23, Switzerland
2
Institiut f¨ur Physik, Johannes Gutenberg-Universit¨at, D-55099 Mainz, Germany
3
School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, UK
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belongs to the lanthanides which have ionization potentials (IP) of relatively low values in the range 5.4 - 6.3 eV [5]. Europium, with an IP of 5.67 eV [6], has therefore been produced at ISOLDE with a standard surface ion source [7] in the past. The effective ionization potential of europium lies at ∼ 5.60 eV,1 which is slightly higher than the effective ionization potential of e.g. samarium (∼ 5.55 eV). For samarium earlier measurements during on-line beam production at ISOLDE have shown, that an enhancement from laser to surface ionization of a factor of 6 can be reached (target at 2000◦ C, ion source at 1600◦ C). Another rare earth element for which resonance laser ionization has been used in the past for on-line applications is neodymium with an effective ionization potential of ∼ 5.43 eV. Depending on the target and ion source temperatures, laser to surface ionization enhancement factors of 3 (target at 1800◦ C, ion source at 2130◦ C) up to 20 have been observed (target at 1800◦ C, ion source at 1930◦ C). It is therefore reasonable to expect that a significant enhancement factor in the ion rate of europium shou
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