Masses of neutron-rich ${}^{52-54}$Sc and ${}^{54,56}$Ti nuclides: The $N=32$ subshell closure in scandium

Abstract

Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the neutron-rich ${}^{52-54}$Sc and ${}^{54,56}$Ti nuclei. The new mass excess values $ME$(${}^{52}$Sc) $=$ $-40525(65)$ keV, $ME$(${}^{53}$Sc) $=$ $-38910(80)$ keV, and $ME$(${}^{54}$Sc) $=$ $-34485(360)$ keV, deviate from the Atomic Mass Evaluation 2012 by 2.3$\sigma$, 2.8$\sigma$, and 1.7$\sigma$, respectively. These large deviations significantly change the systematics of the two-neutron separation energies of scandium isotopes. The empirical shell gap extracted from our new experimental results shows a significant subshell closure at $N=32$ in scandium, with a similar magnitude as in calcium. Moreover, we present $ab$ $initio$ calculations using the valence-space in-medium similarity renormalization group based on two- and three-nucleon interactions from chiral effective field theory. The theoretical results confirm the existence of a substantial $N=32$ shell gap in Sc and Ca with a decreasing trend towards lighter isotones, thus providing a consistent picture of the evolution of the $N=32$ magic number from the $pf$ into the $sd$ shell.

arXiv comment6 pages, 5figures, accepted by Physical Review C

References in corpus (23)

• Accurate Charge-Dependent Nucleon-Nucleon Potential at Fourth Order of Chiral Perturbation Theory
• Improved nuclear matter calculations from chiral low-momentum interactions
• The In-Medium Similarity Renormalization Group: A Novel Ab Initio Method for Nuclei
• A nucleus-dependent valence-space approach to nuclear structure
• Structure of the lightest tin isotopes
• Nonperturbative shell-model interactions from the in-medium similarity renormalization group
• Saturation with chiral interactions and consequences for finite nuclei
• In-Medium Similarity Renormalization Group for Open-Shell Nuclei
• The Magnus expansion and the in-medium similarity renormalization group
• Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K
• New precision mass measurements of neutron-rich calcium and potassium isotopes and three-nucleon forces
• Ground and excited states of doubly open-shell nuclei from ab initio valence-space Hamiltonians
• Dawning of the N=32 shell closure seen through precision mass measurements of neutron-rich titanium isotopes
• Exploring sd-shell nuclei from two- and three-nucleon interactions with realistic saturation properties
• Precision Mass Measurement of ${}^{58-63}$Cr: Nuclear Collectivity towards the \emph{N}=40 Island of Inversion
• Isochronous mass measurements of $T_z=-1$ $fp$-shell nuclei from projectile fragmentation of ${}^{58}$Ni
• Storage ring mass spectrometry for nuclear structure and astrophysics research
• Time-of-flight mass measurements for nuclear processes in neutron star crusts
• Identification of the Lowest $T=2$, $J^{\pi =}{0}^{+}$ Isobaric Analog State in ${}^{52}$Co and Its Impact on the Understanding of $\beta$-Decay Properties of ${}^{52}$Ni
• Direct mass measurements of neutron-rich ${}^{86}$Kr projectile fragments and the persistence of neutron magic number $N$ = 32 in Sc isotopes
• Mass measurement of 56Sc reveals a small A=56 odd-even mass staggering, implying a cooler accreted neutron star crust
• Structure of 55Sc and development of the N=34 subshell closure
• Spectroscopy of ${}^{50}$Sc and ab initio calculations of $B(M3)$ strengths

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• Mass measurements for $T_z=-2$ $fp$-shell nuclei ${}^{40}$Ti, ${}^{44}$Cr, ${}^{46}$Mn, ${}^{48}$Fe, ${}^{50}$Co and ${}^{52}$Ni
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• Isospin dependent properties of the isotopic chain of Scandium and Titanium nuclei within the relativistic mean-field formalism
• Potential signature of new magicity from universal aspects of nuclear charge radii
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• Evolution of shell structure at $\mathbf{N}=32$ and 34: Insights from realistic nuclear forces