Evidence for a Change in the Nuclear Mass Surface with the Discovery of the Most Neutron-Rich Nuclei with 17≤Z≤25

The results of measurements of the production of neutron-rich nuclei by the fragmentation of a Ge76 beam are presented. The cross sections were measured for a large range of nuclei including 15 new isotopes that are the most neutron-rich nuclides of the elements chlorine to manganese (Cl50, Ar53, K55,56, Ca57,58, Sc59,60,61, Ti62,63, V65,66, Cr68, Mn70). The enhanced cross sections of several new nuclei relative to a simple thermal evaporation framework, previously shown to describe similar production cross sections, indicates that nuclei in the region around Ti62 might be more stable than predicted by current mass models and could be an indication of a new island of inversion similar to that centered on Na31.