Observation of positive-parity bands in ${}^{109}$Pd and ${}^{111}$Pd: Enhanced $\ensuremath{\gamma}$ softness

Observation of positive-parity bands in $^{109}$ Pd and $^{111}$ Pd: Enhanced $γ$ softness

E. A. Stefanova, S. Lalkovski, A. Korichi, T. Kutsarova, A. Lopez-Martens, F. R. Xu, H. L. Liu, S. Kisyov, A. Minkova, D. Bazzacco, M. Bergström, A. Görgen, F. Hannachi, B. Herskind, H. Hübel, A. Jansen, T. L. Khoo, Zs. Podolyák, and G. Schönwasser

Phys. Rev. C 86, 044302 – Published 1 October 2012

Abstract

The neutron-rich nuclei $^{109}$ Pd and $^{111}$ Pd were produced as fission fragments following the $^{30} Si +^{168} Er$ reaction at 142 MeV. Using the identification based on the coincidences with the complementary fission fragments, the only positive-parity bands observed so far in $^{109}$ Pd and $^{111}$ Pd emerged from this work. A band, built on top of the 5/2 $^{+}$ ground state exhibiting $Δ I = 1$ energy-level staggering, was observed in each of these nuclei. Both nuclei of interest, $^{109}$ Pd and $^{111}$ Pd, are suggested to lie in the transitional region of Pd isotopes of maximum $γ$ softness. The ground states of both nuclei are predicted by total Routhian surface calculations to be extremely $γ$ soft with shallow triaxial minima. The first crossing in the new bands is proposed to be attributable to an alignment of $h_{11 / 2}^{2}$ neutrons.

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Received 28 March 2012

DOI:https://doi.org/10.1103/PhysRevC.86.044302

Authors & Affiliations

E. A. Stefanova^1,*, S. Lalkovski², A. Korichi³, T. Kutsarova¹, A. Lopez-Martens³, F. R. Xu⁴, H. L. Liu⁴, S. Kisyov², A. Minkova², D. Bazzacco⁵, M. Bergström⁶, A. Görgen^7,†, F. Hannachi^3,‡, B. Herskind⁶, H. Hübel⁷, A. Jansen⁷, T. L. Khoo⁸, Zs. Podolyák^9,§, and G. Schönwasser⁷

¹Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Science, 1784 Sofia, Bulgaria
²Faculty of Physics, University of Sofia “St. Kliment Ohridski,” 1164 Sofia, Bulgaria
³CSNSM Orsay, IN2P3/CNRS, F-91405, France
⁴School of Physics, Peking University, Beijing 100871, China
⁵INFN, Sezione di Padova, I-35131 Padova, Italy
⁶The Niels Bohr Institut, Blegdamsvej 17, DK-2100 Copenhagen, Denmark
⁷Helmholtz-Institut für Strahlen -und Kernphysik, Universität Bonn, Nussallee 14-16, D-53115 Bonn, Germany
⁸Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
⁹INFN, Laboratori Nazionali di Legnaro, I-35020 Padova, Italy

^*elenas@inrne.bas.bg
^†Present address: DAPNIA/SPhN, CEA-Saclay, Gif-sur-Yvette, France.
^‡Present address: Centre d'Etudes Nuclaires de Bordeaux-Gradignan, Gradignan, France.
^§Present address: Department of Physics, University of Surrey, Guildford GU27XH, UK.

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Vol. 86, Iss. 4 — October 2012

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Physical Review C

covering nuclear physics

Observation of positive-parity bands in $^{109}$ Pd and $^{111}$ Pd: Enhanced $γ$ softness

E. A. Stefanova, S. Lalkovski, A. Korichi, T. Kutsarova, A. Lopez-Martens, F. R. Xu, H. L. Liu, S. Kisyov, A. Minkova, D. Bazzacco, M. Bergström, A. Görgen, F. Hannachi, B. Herskind, H. Hübel, A. Jansen, T. L. Khoo, Zs. Podolyák, and G. Schönwasser

Phys. Rev. C 86, 044302 – Published 1 October 2012

Abstract

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Physical Review C

covering nuclear physics

Observation of positive-parity bands in 109Pd and 111Pd: Enhanced γ softness

E. A. Stefanova, S. Lalkovski, A. Korichi, T. Kutsarova, A. Lopez-Martens, F. R. Xu, H. L. Liu, S. Kisyov, A. Minkova, D. Bazzacco, M. Bergström, A. Görgen, F. Hannachi, B. Herskind, H. Hübel, A. Jansen, T. L. Khoo, Zs. Podolyák, and G. Schönwasser

Phys. Rev. C 86, 044302 – Published 1 October 2012

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Observation of positive-parity bands in $^{109}$ Pd and $^{111}$ Pd: Enhanced $γ$ softness