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

Phys. Lett. B

647
237
(2007)
P. Doornenbal, P. Reiter, H. Grawe, T. Otsuka, A. Al-Khatib, A. Banu, T. Beck, F. Becker, P. Bednarczyk, G. Benzoni, A. Bracco, A. Bürger, L. Caceres, F. Camera, S. Chmel, F.C.L. Crespi, H. Geissel, J. Gerl, M. Górska, J. Grebosz, H. Hübel, M. Kavatsyuk, O. Kavatsyuk, M. 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

The first excited 
2
+
 state of 36Ca has been identified by its γ-decay, exploiting the two-step fragmentation technique at the FRS-RISING setup at GSI. This is the heaviest 
𝑇
𝑧
=
−
2
 nucleus in the Segré chart in which a γ-decay of an excited state has been observed. A stable beam of 40Ca at 
420
𝐴
MeV
 impinged on a primary 9Be target. Out of the secondary beam of fragmentation products, 37Ca was separated by the FRS and struck on a second 9Be target at the final focus of the FRS. The energy for the 
2
1
+
 decay of 36Ca was determined to be 3015(16) keV, which is 276 keV lower than in its 
𝑇
=
2
 mirror 36S. This mirror energy difference (MED) is discussed in the framework of shell model calculations using a 16O core, the sd shell isospin symmetric interaction USD and experimental single-particle energies from 17O and 17F. 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.

DOI
10.1016/j.physletb.2007.02.001
Published on
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