Is N = 40 magic? An analysis of ISOLTRAP mass measurements
Recently high-precision mass measurements were performed on Ni, Cu, and Ga isotopes at the triple-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The relative uncertainty was of the order of 10−8. Data indicate a competition between the sub-shell closure N=40 and the mid-shell region N=39 between the well-known magic numbers N=28 and N=50.