L.-L. Andersson

New Short-Lived Isotope 221U and the Mass Surface Near N=126

Two short-lived isotopes ^{221}U and ^{222}U were produced as evaporation residues in the fusion reaction ^{50}Ti+^{176}Yb at the gas-filled recoil separator TASCA. An α decay with an energy of E_{α}=9.31(5)  MeV and half-life T_{1/2}=4.7(7)  μs was attributed to ^{222}U. The new isotope ^{221}U was identified in α-decay chains starting with E_{α}=9.71(5)  MeV and T_{1/2}=0.66(14)  μs leading to known daughters. Synthesis and detection of these unstable heavy nuclei and their descendants were achieved thanks to a fast data readout system. The evolution of the N=126 shell closure and its influence on the stability of uranium isotopes are discussed within the framework of α-decay reduced width.

Recoil-alpha-fission and Recoil-alpha-alpha-fission Chains Stemming from Element 115

Rudolph, Dirk; Forsberg, Ulrika; Düllmann, C. E.; Golubev, Pavel; Heßberger, F.P.; Khuyagbaatar, J.; Kratz, J. V.; Sarmiento, Luis; Yakushev, A.; Ackermann, D.; Andersson, L.; Block, M.; Brand, H.; Cox, D.; Derkx, X.; Di Nitto, A.; Eberhardt, K.; Even, J.; Fahlander, Claes; Gates, J. M.; Gerl, J.; Gregorich, E. K.; Gross, C. J.; Herzberg, R.-D.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Runke, J.; Rykaczewski, K.; Schädel, M.; Schaffner, H.; Schausten, B.; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Wiehl, N. Published in: GSI Report

Element 115 Studied with TASISpec

D. Rudolph1, U. Forsberg1, P. Golubev1, L.G. Sarmiento1, A. Yakushev2, L.-L. Andersson3, A. Di Nitto4, Ch.E. Dullmann2,3,4, J.M. Gates5, K.E. Gregorich5, C.J. Gross6, R.-D. Herzberg7, F.P. Hesberger2,3, J. Khuyagbaatar3, J.V. Kratz4, K. Rykaczewski6, M. Schadel2,8, S. ◦ Aberg1, D. Ackermann2, M. Block2, H. Brand2, B.G. Carlsson1, D. Cox7, X. Derkx3,4, K. Eberhardt3,4, J. Even3, C. Fahlander1, J. Gerl2, E. Jager2, B. Kindler2, J. Krier2, I. Kojouharov2, N. Kurz2, B. Lommel2, A. Mistry7, C. Mokry3,4, H. Nitsche5, J.P. Omtvedt9, P. Papadakis7, I. Ragnarsson1, J. Runke2, H. Schaffner2, B. Schausten2, P. Thorle-Pospiech3,4, T. Torres2, T. Traut4, N. Trautmann4, A. Turler10, A. Ward7, D.E. Ward1, and N. Wiehl3,4 1Lund University, Lund, Sweden; 2GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt, Germany; 3Helmholtz Institute Mainz, Mainz, Germany; 4Johannes Gutenberg-Universitat Mainz, Mainz, Germany; 5Lawrence Berkeley National Laboratory, Berkeley, USA; 6Oak Ridge National Laboratory, Oak Ridge, USA; 7University of Liverpool, Liverpool, United Kingdom; 8Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan; 9University of Oslo, Oslo, Norway; 10Paul Scherrer Institute and University of Bern, Villigen, Switzerland

Comprehensive {gamma}-ray spectroscopy of rotational bands in the N=Z+1 nucleus {sup 61}Zn

The Zn-61(30)31 nucleus has been studied via the combined data of two fusion-evaporation reaction experiments using a Ar-36 beam and a Si-28 target foil. The experimental setups involved the Ge array GAMMASPHERE and neutron and charged particle detectors placed around the target position. The resulting level scheme comprises about 120 excited states connected via some 180 gamma-ray transitions. In total, seven rotational structures were identified up to I similar to 25 or higher and compared with predictions from cranked Nilsson-Strutinsky calculations.

Characterization of superdeformed bands in {sup 62}Zn

Combined data from four fusion-evaporation reaction experiments were utilized to investigate deformed and superdeformed structures in Zn-62(30)32. Combination of the Gammasphere gamma-ray spectrometer and ancillary particle detection systems allowed for the connection of rotational bands to well-known, low-lying excited states in Zn-62, as well as spectroscopy of discrete high-spin states reaching excitation energies of E-x=42.5 MeV. Four well- or superdeformed bands in Zn-62 are characterized and described by means of cranked Nilsson-Strutinsky calculations.

Classification of Superdeformed Bands in the Mass A~60 Region

The experimental knowledge of the Cu-61(29)32 and Zn-61(30)31 nuclei has been largely extended via the joint results from three experiments. The fusion-evaporation reaction used a Ar-36 beam and a Si-28 target foil to produce the two nuclei via the evaporation of either three protons (Cu-61) or two protons and a neutron (Zn-61). The experimental set-ups comprised the Ge-array GAMMASPHERE as well as neutron and charged-particle detectors placed around the target position. The resulting level schemes include around ten rotational superdeformed structures in each isotope. Most of them are linked to normally deformed states and in many cases spins and parities of the low-lying states in each structure have been determined. The collective structures are compared with results from configuration dependent Cranked Nilsson-Strutinsky calculations. The different structures are in general well understood from the calculation but the results do also suggest modifications of the standard Nilsson parameters in the mass A similar to 60 region. (Less)

Prompt Proton Decay in the Vicinity of 56Ni

A new decay mode, the so called prompt proton decay, was discovered in 1998. It has since proven to be an important decay mechanism for several neutron deficient nuclei in the A similar to 60 region. To measure with high accuracy the energies and angular distributions of these protons, a state-of-the-art charged particle detector - LuWuSiA - was developed. It was first utilized during a fusion-evaporation reaction experiment performed at Argonne National Laboratory, U.S.A. In this contribution, the characteristics of the prompt proton decay are discussed along with the special features of LuWuSiA as well as a revisit to the prompt proton decay in Cu-58.