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

• Published in: Physics letters. B Vol. 647; no. 4; pp. 237 - 242
• Main Authors: Doornenbal, P., Reiter, P., Grawe, H., Otsuka, T., Al-Khatib, A., Banu, A., Beck, T., Becker, F., Bednarczyk, P., Benzoni, G., Bracco, A., Bürger, A., Caceres, L., Camera, F., Chmel, S., Crespi, F.C.L., Geissel, H., Gerl, J., Górska, M., Grȩbosz, J., Hübel, H., Kavatsyuk, M., Kavatsyuk, O., Kmiecik, M., Kojouharov, I., Kurz, N., Lozeva, R., Maj, A., Mandal, S., Meczynski, W., Million, B., Podolyák, Zs, Richard, A., Saito, N., Saito, T., Schaffner, H., Seidlitz, M., Striepling, T., Utsuno, Y., Walker, J., Warr, N., Weick, H., Wieland, O., Winkler, M., Wollersheim, H.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 12.04.2007; Elsevier Science
• Subjects: Exact sciences and technology; Nuclear physics; Physics; The physics of elementary particles and fields; 25.70.Mn; 23.20.Lv; 21.60.Cs; Isospin; Shell models; Excited states; Fragmentation
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2007.02.001

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 Tz=−2 nucleus in the Segré chart in which a γ-decay of an excited state has been observed. A stable beam of 40Ca at 420AMeV 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 21+ 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.