Study of the N=50 major shell effect close to ${}^{78}$Ni : First evidence of a weak coupling structure in ${}^{83}\_32$Ge$\_51$ and three-proton configuration states in ${}^{81}\_31$Ga$\_50$

Abstract

New levels were attributed to ${}^{81}\_31$Ga$\_50$ and ${}^{83}\_32$Ge$\_51$ which were fed by the ${\hat{I}}^2$-decay of their respective mother nuclei ${}^{81}\_30$Zn$\_51$ and ${}^{83}\_31$Ga$\_52$ produced by fission at the "PARRNe" ISOL set-up installed at the Tandem accelerator of the Institut de Physique Nucléaire, Orsay. We show that the low energy structure of ${}^{81}\_31$Ga$\_50$ and ${}^{83}\_32$Ge$\_51$ can easily be explained within the natural hypothesis of a strong energy gap at N=50 and a doubly-magic character for ${}^{78}$Ni.

2 pages, pdf file, To be published in the Proceedings of "International Symposium on Structure of Exotic Nuclei and Nuclear Forces (SENUF 06)", March 2006, Tokyo, Japan