Extinction of the N=20 neutron-shell closure for 32Mg examined by direct mass measurements

Abstract

The 'island of inversion' around ${}^{32}$Mg is one of the most important paradigm for studying the disappearance of the stabilizing 'magic' of a shell closure. We present the first Penning-trap mass measurements of the exotic nuclides ${}^{29-31}$Na and ${}^{30-34}$Mg, which allow a precise determination of the empirical shell gap for ${}^{32}$Mg. The new value of 1.10(3) MeV is the lowest observed shell gap for any nuclide with a canonical magic number.

6 pages, 4 figures, submitted to Physical Review C