Göttingen 1997 – wissenschaftliches Programm
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HK: Hadronen und Kerne
HK 51: Kernspektroskopie, mittelschwere Kerne III
HK 51.5: Gruppenbericht
Mittwoch, 26. März 1997, 18:30–19:00, HS E
Accurate mass measurements of unstable rare earth isotopes with ISOLTRAP — •F. Ames1, G. Audi2, D. Beck3, G. Bollen4, H.-J. Kluge3, A. Kohl3, M. König3, D. Lunney2, R.B. Moore5, H. Raimbault-Hartmann4, E. Schark1, S. Schwarz3, M. de Saint Simon2, J. Szerypo6, and the ISOLDE Collaboration4 — 1Institut für Physik, Universität Mainz, D-55099 Mainz, Germany — 2CSNSM-IN2P3-CNRS, F-91405 Orsay-Campus, France — 3GSI, Postfach 110552, D-65220 Darmstadt, Germany — 4CERN, CH-1211 Geneva, Switzerland — 5Foster Radiation Laboratory, McGill University, Montreal, H3A 2B1, Canada — 6Institute of Experimental Physics, Warsaw-University, PL-00681 Warsaw, Poland
The ISOLTRAP system installed at the on-line mass separator ISOLDE /CERN is a tandem Penning trap mass spectrometer. The first of the two traps serves for accumulation, bunching and cooling of the ions delivered by ISOLDE. In addition this cooler trap acts as an isobar separator, which removes isobaric contaminations as they are present in the ISOLDE beams in the case of rare earth isotopes. The accurate mass determination is performed in the second trap and is carried out via the measurement of the cyclotron frequency of the stored ions. A mass resolving power up to 3 million enables separation of nuclei in their isomeric or ground states as well as isobars. For short-lived isotopes with half-lifes down to one second and a mass of m ≈ 100 u an accuracy of typically δ m / m ≈ 1 · 10−7 is achieved.
Recently, highly accurate mass measurements of neutron deficient rare earth isotopes in the vicinity of 146Gd have been performed. The semi doubly-magic nucleus 146Gd and isotopes surrounding have been of considerable interest for many years. The investigation of the strength of the proton sub-shell closure at Z = 64 and the delivery of reliable and highly accurate ground state masses (δ m < 20 keV) as input data for model calculations are the motivation for the measurements in this region. More than 40 isotopes of the elements Pr, Nd, Pm, Sm, Eu, Dy and Ho have been measured with an typical accuracy of δ m ≈ 14 keV. Some of these isotopes provide an important anchor for many other isotopes linked by known Q-values.