Precision Mass Measurements of Neutron-Rich Scandium Isotopes Refine the Evolution of N=32 and N=34 Shell Closures

• Published in: Physical review letters Vol. 126; no. 4; p. 042501
• Main Authors: Leistenschneider, E, Dunling, E, Bollen, G, Brown, B A, Dilling, J, Hamaker, A, Holt, J D, Jacobs, A, Kwiatkowski, A A, Miyagi, T, Porter, W S, Puentes, D, Redshaw, M, Reiter, M P, Ringle, R, Sandler, R, Sumithrarachchi, C S, Valverde, A A, Yandow, I T
• Format: Journal Article
• Language: English
• Published: United States 29.01.2021
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.126.042501

We report high-precision mass measurements of ^{50-55}Sc isotopes performed at the LEBIT facility at NSCL and at the TITAN facility at TRIUMF. Our results provide a substantial reduction of their uncertainties and indicate significant deviations, up to 0.7 MeV, from the previously recommended mass values for ^{53-55}Sc. The results of this work provide an important update to the description of emerging closed-shell phenomena at neutron numbers N=32 and N=34 above proton-magic Z=20. In particular, they finally enable a complete and precise characterization of the trends in ground state binding energies along the N=32 isotone, confirming that the empirical neutron shell gap energies peak at the doubly magic ^{52}Ca. Moreover, our data, combined with other recent measurements, do not support the existence of a closed neutron shell in ^{55}Sc at N=34. The results were compared to predictions from both ab initio and phenomenological nuclear theories, which all had success describing N=32 neutron shell gap energies but were highly disparate in the description of the N=34 isotone.