Dawning of the N=32 shell closure seen through precision mass measurements of neutron-rich titanium isotopes

A precision mass investigation of the neutron-rich titanium isotopes 51−55Ti was performed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the N ¼ 32 shell closure, and the overall uncertainties of the 52−55Ti mass values were significantly reduced. Our results
conclusively establish the existence of the weak shell effect at N ¼ 32, narrowing down the abrupt onset of this shell closure. Our data were compared with state-of-the-art ab initio shell model calculations which, despite very successfully describing where the N ¼ 32 shell gap is strong, overpredict its strength and extent in titanium and heavier isotones. These measurements also represent the first scientific results of TITAN using the newly commissioned multiple-reflection time-of-flight mass spectrometer, substantiated
by independent measurements from TITAN’s Penning trap mass spectrometer.