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 ⁷⁶Ge 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 (⁵⁰Cl, ⁵³Ar, ^55,56K, ^57,58Ca, ^59,60,61Sc, ^62,63Ti, ^65,66V, ⁶⁸Cr, ⁷⁰Mn). 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 ⁶²Ti 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 ³¹Na.