The T=2 mirrors Ca-36 and S-36: A test for isospin symmetry of shell gaps at the driplines

P. Doornenbal, P. Reiter*, H. Grawe, T. Otsuka, A. Al-Khatib, A. Banu, T. Beck, F. Becker, P. Bednarczyk, G. Benzoni, A. Bracco, A. Buerger, L. Caceres, F. Camera, S. Chmel, M. Gorska, J. Grebosz, H. Huebel, M. Kavatsyuk, O. KavatsyukM. Kmiecik, I. Kojouharov, N. Kurz, R. Lozeva, A. Maj, S. Mandal, W. Meczynski, B. Million, Zs. Podolyak, A. Richard, N. Saito, T. Saito, H. Schaffner, M. Seidlitz, T. Striepling, Y. Utsuno, J. Walker, N. Warr, H. Weick, O. Wieland, M. Winkler, H. J. Wollersheim

*Corresponding author for this work

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Abstract

The first excited 2(+) state of Ca-36 has been identified by its gamma-decay, exploiting the two-step fragmentation technique at the FRS-RISING setup at GSI. This is the heaviest T-Z = -2 nucleus in the Segre chart in which a gamma-decay of an excited state has been observed. A stable beam of Ca-40 at 420A MeV impinged on a primary Be-9 target. Out of the secondary beam of fragmentation products, Ca-37 was separated by the FRS and struck on a second Be-9 target at the final focus of the FRS. The energy for the 2(1)(+) decay of Ca-36 was determined to be 3015(16) keV, which is 276 keV lower than in its T = 2 mirror S-36. This mirror energy difference (MED) is discussed in the framework of shell model calculations using a O-16 core, the sd shell isospin symmetric interaction USD and experimental single-particle energies from O-17 and F-17. The results show that the MED within the sd shell provide a sensitive test for the evolution of the N, Z = 14, 16 subshell gaps towards the driplines. Especially the N, Z = 16 gap is determined by Thomas-Ehrman shift in the A = 17, T = 1/2 isospin doublet, while Coulomb effects are found to have marginal influence. (c) 2007 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)237-242
Number of pages6
JournalPhysics Letters B
Volume647
Issue number4
DOIs
Publication statusPublished - 12-Apr-2007
Externally publishedYes

Keywords

  • EXCITED-STATES
  • NEUTRON
  • NUCLEI
  • IDENTIFICATION
  • SPECTROSCOPY
  • ISOTOPES
  • DECAY
  • MODEL

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