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

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.

Authors: 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

Doi: 10.1016/j.physletb.2007.02.001

Issue number:

Journal: Phys. Lett. B

Page number: 237

Published on: 2007-04-12

Year: