Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in At-217,At-218,At-219 have been measured at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy technique. Magnetic dipole and electric quadrupole moments, and changes in the nuclear mean-square charge radii, have been deduced. A large inverse odd-even staggering in radii, which may be associated with the presence of octupole collectivity, has been observed. Namely, the radius of the odd-odd isotope At-218 has been found to be larger than the average of its even-N neighbors, At-217,At-219. The discrepancy between the additivity-rule prediction and experimental data for the magnetic moment of At-218 also supports the possible presence of octupole collectivity in the considered nuclei.

A. E. Barzakh,1,* J. G. Cubiss,2 A. N. Andreyev,2,3,4 M. D. Seliverstov,1,2 B. Andel,5 S. Antalic,5 P. Ascher,6 D. Atanasov,6 D. Beck,7 J. Bieroń,8 K. Blaum,6 Ch. Borgmann,6 M. Breitenfeldt,9 L. Capponi,10 T. E. Cocolios,4,11 T. Day Goodacre,4,11 X. Derkx,10,12 H. De Witte,9 J. Elseviers,9 D. V. Fedorov,1 V. N. Fedosseev,4 S. Fritzsche,13,14 L. P. Gaffney,9 S. George,6 L. Ghys,9,15 F. P. Heßberger,16,17 M. Huyse,9 N. Imai,4,18 Z. Kalaninová,5,19 D. Kisler,6 U. Köster,20 M. Kowalska,4 S. Kreim,6,4 J. F. W. Lane,10 V. Liberati,10 D. Lunney,21 K. M. Lynch,4,11 V. Manea,4,21 B. A. Marsh,4 S. Mitsuoka,3 P. L. Molkanov,1 Y. Nagame,3 D. Neidherr,7 K. Nishio,3 S. Ota,3 D. Pauwels,15 L. Popescu,15 D. Radulov,9 E. Rapisarda,4 J. P. Revill,22 M. Rosenbusch,23,24 R. E. Rossel,4,25 S. Rothe,4,25 K. Sandhu,10 L. Schweikhard,23 S. Sels,9 V. L. Truesdale,2 C. Van Beveren,9 P. Van den Bergh,9 P. Van Duppen,9 Y. Wakabayashi,3 K. D. A. Wendt,25 F. Wienholtz,23,4 B. W. Whitmore,2 G. L. Wilson,2 R. N. Wolf,6,† and K. Zuber26 1Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, 188300 Gatchina, Russia 2Department of Physics, University of York, York, YO10 5DD, United Kingdom 3Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-Mura, Naka-gun, Ibaraki 319–1195, Japan 4CERN, CH-1211 Geneva 23, Switzerland 5Department of Nuclear Physics and Biophysics, Comenius University in Bratislava, 84248 Bratislava, Slovakia 6Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany 7GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany 8Instytut Fizyki imienia Mariana Smoluchowskiego, Uniwersytet Jagielloński, ul. prof. Stanisława Łojasiewicza 11, Kraków, Poland 9KU Leuven, Instituut voor Kernen Stralingsfysica, B-3001 Leuven, Belgium 10School of Engineering, University of the West of Scotland, Paisley PA1 2BE, United Kingdom 11School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, United Kingdom 12LPC, ENSICAEN, Université de Caen Basse Normandie, CNRS/IN2P3-ENSI, Caen F-14050, France 13Helmholtz-Institut Jena, Fröbelstieg 3, D-07743 Jena, Germany 14Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena, Germany 15Belgian Nuclear Research Center SCKCEN, Boeretang 200, B-2400 Mol, Belgium 16Gesellschaft für Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt, Germany 17Helmholtz Institut Mainz, 55099 Mainz, Germany 18High Energy Accelerator Research Organisation (KEK), Oho 1-1, Tsukuba, Ibaraki 305–0801, Japan 19Laboratory of Nuclear Problems, JINR, 141980 Dubna, Russia 20Institut Laue Langevin, 71 avenue des Martyrs, F-38042 Grenoble Cedex 9, France 21CSNSM-IN2P3-CNRS, Université Paris-Sud, 91406 Orsay, France 22Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE, United Kingdom 23Universität Germany, Institut für Physik, 17487 Greifswald, Germany 24RIKEN Nishina Center for Accelerator-Based Science, Wako, 351-098 Saitama, Japan 25Institut für Physik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany 26Technische Universität Dresden, 01069 Dresden, Germany

Hyperfine-structure parameters and isotope shifts of At195-211 have been measured for the first time at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy method. The hyperfine structures of isotopes were recorded using a triad of experimental techniques for monitoring the photo-ion current. The Multi-Reflection Time-of-Flight Mass Spectrometer, in connection with a high-resolution electron multiplier, was used as an ioncounting setup for isotopes that either were affected by strong isobaric contamination or possessed a long half-life; the ISOLDE Faraday cups were used for cases with high-intensity beams; and the Windmill decay station was used for short-lived, predominantly a-decaying nuclei. The electromagnetic moments and changes in the mean-square charge radii of the astatine nuclei have been extracted from the measured hyperfine-structure constants and isotope shifts. This was only made possible by dedicated state-of-the-art large-scale atomic computations of the electronic factors and the specific mass shift of atomic transitions in astatine that are needed for these extractions. By comparison with systematics, it was possible to assess the reliability of the results of these calculations and their ascribed uncertainties. A strong deviation in the ground-statemean-square charge radii of the lightest astatine isotopes, from the trend of the (spherical) lead isotopes, is interpreted as the result of an onset of deformation. This behavior bears a resemblance to the deviation observed in the isotonic polonium isotopes. Cases for shape coexistence have been identified in At-197,At-199, for which a significant difference in the charge radii for ground (9/2(-)) and isomeric (1/2(+)) states has been observed.

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We present a study of nuclear shape coexistence in the region of neutron-deficient lead isotopes. The midshell gold isotopes Au180,185,188,190 (Z=79), the two long-lived nuclear states in At197 (Z=85), and the neutron-rich nuclide At219 were produced by the ISOLDE facility at CERN and their masses were determined with the high-precision Penning-trap mass spectrometer ISOLTRAP. The studied gold isotopes address the trend of binding energies in a region of the nuclear chart where the nuclear charge radii show pronounced discontinuities. Significant deviations from the atomic-mass evaluation were found for Au188,190. The new trend of two-neutron separation energies is smoother, although it does reveal the onset of deformation. The origin of this effect is interpreted in connection to the odd-even staggering of binding energies, as well as theoretically by Hartree-Fock-Bogoliubov calculations including quasiparticle blocking. The role of blocking for reproducing the large odd-even staggering of charge radii in the mercury isotopic chain is illustrated.

Alkali ion beams are among the most intense produced by the ISOLDE facility. These were the first to be studied by the ISOLTRAP mass spectrometer and ever since, new measurements have been regularly reported. Recently the masses of very neutron-rich and short-lived cesium isotopes were determined at ISOLTRAP. The isotope Cs-148 was measured directly for the first time by Penning-trap mass spectrometry. Using the new results, the trend of two-neutron separation energies in the cesium isotopic chain is revealed to be smooth and gradually decreasing, similar to the ones of the barium and xenon isotopic chains. Predictions of selected microscopic models are employed for a discussion of the experimental data in the region.

M. Rosenbusch, P. Ascher, D. Atanasov, C. Barbieri, D. Beck, K. Blaum, Ch. Borgmann, M. Breitenfeldt, R.B. Cakirli, 6 A. Cipollone, S. George, F. Herfurth, M. Kowalska, S. Kreim, 7 D. Lunney, V. Manea, P. Navrátil, D. Neidherr, L. Schweikhard, V. Somà, 11, 12 J. Stanja, F. Wienholtz, R. N. Wolf, 2 and K. Zuber Institut für Physik, Ernst-Moritz-Arndt Universität Greifswald, 17487 Greifswald, Germany Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany Department of Physics, University of Surrey, Guildford GU2 7XH, UK GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany Instituut voor Kernen Stralingsfysica, KU Leuven, Celestijnenlaan 200d, B-3001 Heverlee, Belgium Department of Physics, University of Istanbul, 34134 Istanbul, Turkey CERN, 1211 Geneva 23, Switzerland CSNSM-IN2P3-CNRS, Université Paris-Sud, 91405 Orsay, France TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T 2A3, Canada CEA-Saclay, IRFU/Service de Physique Nucléaire, 91191 Gif-sur-Yvette, France Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany Institut für Kernund Teilchenphysik, Technische Universität Dresden, 01069 Dresden, Germany

The recently confirmed neutron-shell closure at N = 32 has been investigated for the first time below the magic proton number Z = 20 with mass measurements of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide investigated at the online mass spectrometer ISOLTRAP. The resulting two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly lower than for 52Ca, highlighting the doubly-magic nature of this nuclide. Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations are challenged by the new measurements but reproduce qualitatively the observed shell effect.

M. Rosenbusch, P. Ascher, D. Atanasov, C. Barbieri, D. Beck, K. Blaum, Ch. Borgmann, M. Breitenfeldt, R. B. Cakirli, A. Cipollone, S. George, F. Herfurth, M. Kowalska, S. Kreim, D. Lunney, V. Manea, P. Navrátil, D. Neidherr, L. Schweikhard, V. Somà, J. Stanja, F. Wienholtz, R. N. Wolf, and K. Zuber Institut für Physik, Ernst-Moritz-Arndt Universität Greifswald, 17487 Greifswald, Germany Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany Instituut voor Kernen Stralingsfysica, KU Leuven, Celestijnenlaan 200d, B-3001 Heverlee, Belgium Department of Physics, University of Istanbul, 34134 Istanbul, Turkey CERN, 1211 Geneva 23, Switzerland CSNSM-IN2P3-CNRS, Université Paris-Sud, 91405 Orsay, France TRIUMF, 4004 Westbrook Mall, Vancouver, British Columbia V6T 2A3, Canada CEA-Saclay, IRFU/Service de Physique Nucléaire, 91191 Gif-sur-Yvette, France Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany Institut für Kernund Teilchenphysik, Technische Universität Dresden, 01069 Dresden, Germany (Received 31 December 2014; revised manuscript received 14 March 2015; published 20 May 2015)

The success of many measurements in analytical mass spectrometry as well as in precision mass determinations for atomic and nuclear physics is handicapped when the ion sources deliver “contaminations”, i.e., unwanted ions of masses similar to those of the ions of interest. In particular, in ion-trapping devices, large amounts of contaminant ions result in significant systematic errors—if the measurements are possible at all. We present a solution for such cases: The ions from a quasi-continuous source are bunched in a linear radio-frequency-quadrupole ion trap, separated by a multi-reflection time-of-flight section followed by a Bradbury–Nielsen gate, and then captured in a Penning trap. Buffer-gas cooling is used to damp the ion motion in the latter, which allows a repeated opening of the Penning trap for a stacking of mass-selected ion bunches. Proof-of-principle demonstrations have been performed with the ISOLTRAP setup at ISOLDE/CERN, both with 133 Cs + ions from an off-line ion source and by application to an on-line beam of 179 Lu + ions contaminated with 163 Dy 16 O + ions. In addition, an optimization of the experimental procedure is given, in particular for the number of ion bunches captured as a function of the ions’ lifetimes and the parameters of the experiment .

We request 6 extra shifts to complete the experimental program of IS532 (for which 3 shifts remain), by performing mass measurements of the isotopes 52−55Sc with the ISOLTRAP mass spectrometer. The scandium mass measurements, already approved by the INTC, would probe the extension of the N = 32 shell-closure effect, revealed in the mass surface by the successful calcium measurements of this experiment. The program now also benefits from the development of a new mass-measurement technique, which uses the multi-reflection time-of-flight mass spectrometer of ISOLTRAP, and was developed for determining the masses of 53,54Ca. Requested shifts (in total): 9 shifts (6 extra) on a UCx target, with RILIS. The present Addendum follows the status report INTC-SR-034.

The masses of Fr-222,Fr-224,Fr-226-233 and Ra-233,Ra-234 have been determined with the Penning-trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN, including the previously unknown mass and half-life of Fr-233. We study the evolution of the odd-even staggering of binding energies along the francium and radium isotopic chains and of its lowest-order estimator, Delta(3)(N). An enhancement of the staggering of Delta(3)(N) is observed towards neutron number N = 146, which points to contributions beyond pairing correlations. These contributions are investigated in the Hartree-Fock and Hartree-Fock-Bogoliubov approaches, emphasizing the connections to the single-particle level density and nuclear deformation.

High-precision mass measurements of neutron-deficient Tl (A = 184, 186, 190, 193-195, 198) isotopes as well as Pb (A = 202, 208), Fr (A = 207, 208), and Ra (A = 224) are performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The improved precision of the mass data now allows the study of subtle odd-even effects. The gradual development of collectivity with the removal of protons from the magic Z = 82 core is analyzed by combining the new mass results with nuclear charge-radii data and mean-field model predictions.

Recent results from a measurement campaign studying the isomerism in neutron-deficient Tl isotopes are presented. The measurements make use of a nuclear spectroscopy setup coupled to the high-resolution Penningtrap mass spectrometer ISOLTRAP at CERN's radioactive ion-beam facility ISOLDE. The mass values of Tl-190,Tl-194 are improved and a mass-spin-state assignment is carried out. An additional mass measurement of the grandparent nuclide At-198 allows the deduction of the spin-state ordering in Tl-190. As a result, the excitation energies of the isomers in both Tl isotopes are determined for the first time to Eex(Tl-194) = 260(15) keV and E-ex(Tl-190) = 89(12) keV. Furthermore, this allows anchoring of the ground-state and isomer masses of Bi-194, Fr-202, and Ac-206, which are linked by two independent a-decay chains.

Shell effects and their evolution across the nuclear chart pose important constraints on the modelling of the nucleon-nucleon interaction. The strength of shell closures in neutronrich nuclei also influences the path of the r-process of nucleosynthesis and the predicted elemental abundances. We propose to measure the masses of the isotopes 132,133In, 129−132Cd, 125−129Ag with the Penning-trap mass spectrometer ISOLTRAP. The recently developed multi-reflection time-of-flight mass separator of ISOLTRAP will allow, as a beam purifier, to handle higher contamination ratios as before and, for the more exotic cases, to directly determine the mass of the nuclides of interest. The masses of the proposed isotopes will allow the investigation of a possible weakening of the N = 82 shell gap for Z < 50 and corresponding r-process waiting point. This in turn enables an exploration of the impact on the A = 130 r-process abundances. Requested shifts: 50 shifts (split in 3 runs over 2 years)

The Penning-trap mass spectrometer ISOLTRAP, located at the isotope-separator facility ISOLDE (CERN), is presented in its current form taking into account technical developments since 2007. Three areas of developments are presented. The reference ion sources have been modified to guarantee a sufficient supply of reference ions for mass measurements and systematic studies. Different excitation schemes have been investigated for manipulation of the ion motion in the Penning trap, to enhance either the purification or measurement process. A multi-reflection time-of-flight mass separator has been implemented and can now be routinely used for purification and as a versatile tool for beam analysis. (C) 2013 Elsevier B.V. All rights reserved.

Nature 498, 346–349 (2013); doi:10.1038/nature12226 In Fig. 3b of this Letter, the y axis numbering should be identical to that of Fig. 3a, and start at 2 MeV and go up to 25 MeV. Instead, the numbering was inadvertently shifted upwards, which made the data shown in Fig. 3b appear to have higher values by 2 MeV with respect to their actual ones.

The online precision mass spectrometer ISOLTRAP at ISOLDE/CERN was recently upgraded by adding a multi-reflection time-of-flight mass separator/spectrometer (MR-ToF MS) between the linear radio-frequency ion trap and the two Penning traps already in place. As a mass separator, the MR-ToF device has improved significantly ISOLTRAP's capability of purification of contaminated ion beams. In addition, the MR-ToF MS can be operated as a mass spectrometer, either to analyze the ISOLDE ion beam or for precision mass measurements of nuclides that are shorter-lived or that have lower yields than those accessible for Penning-trap mass spectrometry. The MR-ToF MS and corresponding components, its integration into ISOLTRAP, and its various operation modes are reviewed. Furthermore, a precision measurement of the Eu-137 mass is presented, determined with the help of the MR-ToF device as a mass separator. (C) 2013 Elsevier B.V. All rights reserved.

Modeling the composition of neutron-star crusts depends strongly on binding energies of neutron-rich nuclides near the N = 50 and N = 82 shell closures. Using a recent development of time-of-flight mass spectrometry for on-line purification of radioactive ion beams to access more exotic species, we have determined for the first time the mass of (82)Zn with the ISOLTRAP setup at the ISOLDE-CERN facility. With a robust neutron-star model based on nuclear energy-density-functional theory, we solve the general relativistic Tolman-Oppenheimer-Volkoff equations and calculate the neutron-star crust composition based on the new experimental mass. The composition profile is not only altered but now constrained by experimental data deeper into the crust than before.