High-Precision Mass Spectrometry

Abstract: Accounting for the appearance of new magic numbers represents an exacting test for nuclear models. Binding energies offer a clear signature for the presence (or dis-appearance) of shell closures. To determine the strength of the purported N = 32 shell closure, we propose using the Penning-trap spectrometer ISOLTRAP for mass measure-ments of N = 34 isotones 58Cr (Z = 24), 55Sc (Z = 21) and 54Ca (Z = 20), as well as the N = 32 isotones 53Sc and 52Ca. We also propose measuring the mass of 60Cr to test the shell model prediction of a new magic number at N = 34. In addition to the Penning-trap system at ISOLTRAP, we intend to use the newly commissioned multi-reflection time-of-flight mass separator, which enables direct mass measurements on nuclei with half-lives below 50 ms. Requested shifts: We request 20 shifts using a UC (or YO) target with laser ionization. We request 7 additional shifts to develop the new technique of measuring short-lived species using the electrostatic isobar-separator stage of ISOLTRAP. To be scheduled in 3 separate runs. 1