New subshell closure at $N=58$ emerging in neutron-rich nuclei beyond $^{78}\mathrm{Ni}$

New subshell closure at $N = 58$ emerging in neutron-rich nuclei beyond ${}^{78}{Ni}$

J. A. Winger, K. P. Rykaczewski, C. J. Gross, R. Grzywacz, J. C. Batchelder, C. Goodin, J. H. Hamilton, S. V. Ilyushkin, A. Korgul, W. Królas, S. N. Liddick, C. Mazzocchi, S. Padgett, A. Piechaczek, M. M. Rajabali, D. Shapira, E. F. Zganjar, and J. Dobaczewski

Phys. Rev. C 81, 044303 – Published 7 April 2010

Abstract

The structure of neutron-rich nuclei beyond ${}^{78}{Ni}$ was studied using postaccelerated radioactive beams of ${}^{83, 84, 85}{Ga}$ utilizing $β γ$ and $β - n γ$ spectroscopy. Our data, when combined with energy level systematics, suggests a possible new spherical subshell closure at $N = 58$ is created by the nearly degenerated $ν 3 s_{1 / 2}$ and $ν 2 d_{5 / 2}$ orbitals being well separated from other orbitals above $N = 50$ . The near degeneracy of these states could be evidenced by isomerism in this region. The energies of the $2_{1}^{+}$ and proposed $4_{1}^{+}$ states observed in $N = 52$ ${}^{84}{Ge}$ are interpreted as an indication of a possible weakening of the doubly magic ${}^{78}{Ni}$ core for nuclei beyond $N = 50$ . The experimental evidence is supported by spherical HFB calculations using the ${SkO}_{T}$ functional involving the tensor term in the nucleon-nucleon interaction.

Received 15 October 2009

DOI:https://doi.org/10.1103/PhysRevC.81.044303

Authors & Affiliations

J. A. Winger^1,*, K. P. Rykaczewski², C. J. Gross², R. Grzywacz^2,3, J. C. Batchelder⁴, C. Goodin⁵, J. H. Hamilton⁵, S. V. Ilyushkin¹, A. Korgul^3,5,6,7, W. Królas^7,8, S. N. Liddick^3,4, C. Mazzocchi^3,9, S. Padgett³, A. Piechaczek¹⁰, M. M. Rajabali³, D. Shapira², E. F. Zganjar¹⁰, and J. Dobaczewski^11,12

¹Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, USA
²Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
³Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
⁴UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831, USA
⁵Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
⁶Institute of Experimental Physics, Warsaw University, Warszawa PL-00681, Poland
⁷Joint Institute for Heavy-Ion Reactions, Oak Ridge, Tennessee 37831, USA
⁸Institute of Nuclear Physics, Polish Academy of Sciences, Kraków PL-31342, Poland
⁹Università degli Studi di Milano and INFN, Sez. Milano, Milano I-20133, Italy
¹⁰Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
¹¹Institute of Theoretical Physics, Warsaw University, PL-00681 Warsaw, Poland
¹²Department of Physics, FI-40014, University of Jyväskylä, Jyväskylä, Finland

^*j.a.winger@msstate.edu

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Vol. 81, Iss. 4 — April 2010

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Physical Review C

covering nuclear physics

New subshell closure at $N = 58$ emerging in neutron-rich nuclei beyond ${}^{78}{Ni}$

J. A. Winger, K. P. Rykaczewski, C. J. Gross, R. Grzywacz, J. C. Batchelder, C. Goodin, J. H. Hamilton, S. V. Ilyushkin, A. Korgul, W. Królas, S. N. Liddick, C. Mazzocchi, S. Padgett, A. Piechaczek, M. M. Rajabali, D. Shapira, E. F. Zganjar, and J. Dobaczewski

Phys. Rev. C 81, 044303 – Published 7 April 2010

Abstract

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Physical Review C

covering nuclear physics

New subshell closure at N=58 emerging in neutron-rich nuclei beyond Ni78

J. A. Winger, K. P. Rykaczewski, C. J. Gross, R. Grzywacz, J. C. Batchelder, C. Goodin, J. H. Hamilton, S. V. Ilyushkin, A. Korgul, W. Królas, S. N. Liddick, C. Mazzocchi, S. Padgett, A. Piechaczek, M. M. Rajabali, D. Shapira, E. F. Zganjar, and J. Dobaczewski

Phys. Rev. C 81, 044303 – Published 7 April 2010

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New subshell closure at $N = 58$ emerging in neutron-rich nuclei beyond ${}^{78}{Ni}$