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

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

E. Leistenschneider, E. Dunling, G. Bollen, B. A. Brown, J. Dilling, A. Hamaker, J. D. Holt, A. Jacobs, A. A. Kwiatkowski, T. Miyagi, W. S. Porter, D. Puentes, M. Redshaw, M. P. Reiter, R. Ringle, R. Sandler, C. S. Sumithrarachchi, A. A. Valverde, and I. T. Yandow (The LEBIT Collaboration and the TITAN Collaboration)

Phys. Rev. Lett. 126, 042501 – Published 26 January 2021

Abstract

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.

Received 1 June 2020
Revised 28 September 2020
Accepted 14 December 2020

DOI:https://doi.org/10.1103/PhysRevLett.126.042501

Physics Subject Headings (PhySH)

Nuclear binding Nuclear structure & decays Rare & new isotopes Shell model

Nuclear Physics

Authors & Affiliations

E. Leistenschneider ^1,2,*, E. Dunling ^3,4, G. Bollen^1,2,5, B. A. Brown^1,2,5, J. Dilling^3,6, A. Hamaker ^1,2,5, J. D. Holt^3,7, A. Jacobs^3,6, A. A. Kwiatkowski^3,8, T. Miyagi ³, W. S. Porter ^3,6, D. Puentes ^1,2,5, M. Redshaw ^9,2, M. P. Reiter ^3,10,11, R. Ringle ^1,2, R. Sandler⁹, C. S. Sumithrarachchi^1,2, A. A. Valverde¹², and I. T. Yandow^1,2,5 (The LEBIT Collaboration and the TITAN Collaboration)

¹Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA
²National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
³TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
⁴Department of Physics, University of York, York YO10 5DD, United Kingdom
⁵Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
⁶Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
⁷Department of Physics, McGill University, 3600 Rue University, Montréal, Quebec H3A 2T8, Canada
⁸Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
⁹Department of Physics, Central Michigan University, Mount Pleasant, Michigan 48859, USA
¹⁰II. Physikalisches Institut, Justus-Liebig-Universität, 35392 Gießen, Germany
¹¹School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
¹²Department of Physics & Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada