The mirrors Ca and S; A Test for isospin symmetry of shell gaps at the driplines

Doornenbal, P.*; Reiter, P.*; Grawe, H.*; Otsuka, Takaharu*; Al-Khatib, A.*; Banu, A.*; Beck, T.*; Becker, F.*; Bednarczyk, P.*; Benzoni, G.*; Bracco, A.*; Brger, A.*; Cceres, L.*; Camera, F.*; Chmel, S.*; Crespi, F. C. L.*; Geissel, H.*; Gerl, J.*; Grska, M.*; Grbosz, J.*; Hbel, H.*; Kavatsyuk, M.*; Kavatsyuk, O.*; Kmiecik, M.*; Kojouharov, I.*; Kurz, N.*; Lozeva, R.*; Maj, A.*; Mandal, S.*; Meczynski, W.*; Million, B.*; Podolyk, Zs.*; Richard, A.*; Saito, Nami*; Saito, Takehiko*; Schaffner, H.*; Seidlitz, M.*; Striepling, T.*; Utsuno, Yutaka   ; Walker, J.*; Warr, N.*; Weick, H.*; Wieland, O.*; Winkler, M.*; Wollersheim, H. J.*

The first excited state of Ca was measured at GSI for the first time. The measured energy is found to be 3015(16) keV, which is lower than its mirror nucleus S by as large as 276 keV. The structure of those nuclei is studied by the shell model. It is found that those nuclei can be well described by the valence space. The large energy shift between them is caused by the Thomas-Ehrman effect. We presented that the energy shift in the shell region can be explained by the shell model with a phenomenological treatment of the Thomas-Ehrman effect.