J.J. Carroll

Schottky mass measurements of heavy neutron-rich nuclides in the element range 70 <= Z <= 79 at the GSI Experimental Storage Ring

D. Shubina, 2, 3 R.B. Cakirli, 4 Yu.A. Litvinov, 3 K. Blaum, C. Brandau, 5 F. Bosch, J.J. Carroll, R.F. Casten, D.M. Cullen, I.J. Cullen, A.Y. Deo, B. Detwiler, C. Dimopoulou, F. Farinon, H. Geissel, 11 E. Haettner, M. Heil, R.S. Kempley, C. Kozhuharov, R. Knobel, J. Kurcewicz, N. Kuzminchuk, S.A. Litvinov, Z. Liu, R. Mao, C. Nociforo, F. Nolden, Z. Patyk, W.R. Plass, A. Prochazka, M.W. Reed, 15 M.S. Sanjari, 16 C. Scheidenberger, 11 M. Steck, Th. Stohlker, 17, 18 B. Sun, 19 T.P.D. Swan, G. Trees, P.M. Walker, 20 H. Weick, N. Winckler, 3 M. Winkler, P.J. Woods, T. Yamaguchi, and C. Zhou Max-Planck-Institut fur Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany Fakultat fur Physik und Astronomie, Universitat Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany GSI Helmholtzzentrum fur Schwerionenforschung, Planckstrase 1, 64291 Darmstadt, Germany Department of Physics, University of Istanbul, Istanbul, Turkey ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fur Schwerionenforschung, 64291 Darmstadt, Germany US Army Research Laboratory, 2800 Powder Mill Road, Adelphi MD, USA Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520, USA Schuster Laboratory, University of Manchester, Manchester M13 9PL, United Kingdom Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom Youngstown State University, One University Plaza, Youngstown, Ohio 44555, USA II Physikalisches Institut, Justus-Liebig-Universitat Giesen, 35392 Giesen, Germany School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, People’s Republic of China National Centre for Nuclear Research, PL-00681 Warsaw, Poland Department of Nuclear Physics, R.S.P.E., Australian National University, Canberra ACT 0200, Australia Goethe-Universitat Frankfurt, 60438 Frankfurt, Germany Friedrich-Schiller-Universitat Jena, 07737 Jena, Germany Helmholtz-Institut Jena, 07743 Jena, Germany School of Physics and Nuclear Energy Engineering, Beihang University, 100191 Beijing, PRC CERN, CH-1211 Geneva 23, Switzerland Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan Storage-ring mass spectrometry was applied to neutron-rich Au projectile fragments. Masses of Lu, Hf, Ta, W, and Re nuclei were measured for the first time. The uncertainty of previously known masses of W and Os nuclei was improved. Observed irregularities on the smooth two-neutron separation energies for Hf and W isotopes are linked to the collectivity phenomena in the corresponding nuclei.

Direct observation of long-lived isomers in 212Bi.

Long-lived isomers in (212)Bi have been studied following (238)U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of (212)Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.

Technique for Resolving Low-lying Isomers in the Experimental Storage Ring (ESR) and the Occurrence of an Isomeric State in 192Re

A recent experiment using projectile fragmentation of a 197Au beam on a 9Be target, combined with the fragment recoil separator and experimental storage ring at ring at GSI, has uncovered an isomeric state in 192Re at 267(10) keV with a half-life of ~60 s. The data analysis technique used to resolve the isomeric state from the ground state is discussed.

Direct observation of long-lived isomers in Bi212

Long-lived isomers in (212)Bi have been studied following (238)U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of (212)Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.

Low-lying states near the isomer in

The low-lying states of 108Ag near the I π = 6+ isomer have been investigated with the 11B + 100Mo reaction at 39 MeV beam energy. We aim at understanding the structure of the states near the isomer and identifying possible isomer depletion paths. From the γ–γ and γ–γ–γ coincidence analysis, spectroscopy of the excited states near the isomer has been carried out to establish new transitions and modification of the previously known level scheme. The present work suggests a total of three possible transitions at energies below 500 keV from the isomer to higher excited levels, whose subsequent decay can branch to the ground state. The spins and parities of these states have been established with angular correlation and polarization measurements. The branching ratios and multipolarities of the associated γ-rays were used in the estimation of the integral cross section for induced isomer depletion via these states. The experimental data have been compared to the results of projected Hartree–Fock calculations to understand the configurations of the levels.

Increased lifetime of hydrogen-like

A. Akber1, M.W. Reed1, P.M. Walker2, I.J. Cullen2, Yu.A. Litvinov3,4,5, K. Blaum3,5, F. Bosch4, C. Brandau4,6, J.J. Carroll7, D.M. Cullen8, A.Y. Deo2, B. Detwiler9, C. Dimopoulou4, G.D. Dracoulis1, F. Farinon4, H. Geissel4,10, E. Haettner10, M. Heil4, R.S. Kempley2, T. Kibédi1, R. Knöbel4,10, C. Kozhuharov4, J. Kurcewicz4,11, N. Kuzminchuk4,10, G.J Lane1, S. Litvinov4, Z. Liu12,13, R. Mao13, C. Nociforo4, F. Nolden4, W.R. Plass4,10, A. Prochazka4, C. Scheidenberger4,10, D. Shubina3,5, M. Steck4, Th. Stöhlker4,14,15, B. Sun4, T.P.D. Swan2, G. Trees9, H. Weick4, N. Winckler3,4, M. Winkler4, P.J. Woods12, and T. Yamaguchi16 1Department of Nuclear Physics, R.S.P.E., Australian National University, Canberra ACT 0200, Australia; 2Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom; 3Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany; 4GSI Helmholtzzentrum für Schwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany; 5Physikalisches Institut, Universität Heidelberg, 69120 Heidelberg, Germany; 6ExtreMe Matter Institute EMMI, 64291 Darmstadt, Germany; 7US Army Research Laboratory, 2800 Powder Mill,Road, Adelphi MD, USA; 8Schuster Laboratory, University of Manchester, Manchester M13 9PL, United Kingdom; 9Youngstown State University, One University Plaza, Youngstown, Ohio 44555, USA; 10II Physikalisches Institut, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany; 11CERN, 1211 Geneva 23, Switzerland; 12School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom; 13Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China; 14Institute of Physics, Friedrich-Schiller-Universität Jena, 07743 Jena, Germany; 15Helmholtz-Institut Jena, Fröbelstieg 3, 07743 Jena, Germany; 16Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan Using the Experimental Storage Ring (ESR) it is possible to distinguish between charge states of an isotope with sensitivity down to single ions [1]. Projectile fragmentation of a Au beam (478-492 A·MeV) with a Be target was performed and the resultant fragments were passed through the FRagment Separator [2] where isotopes of interest were separted before being injected into the ESR. The ions were cooled by electron and stochastic cooling enabling Schottky Mass Spectrometry to be used and nuclear decays within the ESR are inferred from changes in ion revolution frequency [3]. Prior studies of Os revealed an isomer with a lifetime of τneut = 8.5(14) s at 2015 keV. Three decay branches have been observed with transition energies of 47, 302, and 307 keV [4]. Neutral [5] and hydrogen-like internal conversion coefficients were calculated and indicate a decrease for all transitions (Table 1). For the 47 keV transition internal conversion in the hydrogen-like state is forbidden. An increased lifetime of τcalc = 13.0(24) s due to the reduction of internal conversion can be expected.