A new study of the $N=32$ and $N=34$ shell gap for Ti and V by the first high-precision MRTOF mass measurements at BigRIPS-SLOWRI

Abstract

The atomic masses of ${}^{55}$Sc, ${}^{56,58}$Ti, and ${}^{56-59}$V have been determined using the high-precision multi-reflection time-of-flight technique. The radioisotopes have been produced at RIKEN's RIBF facility and delivered to the novel designed gas cell and multi-reflection system (ZD MRTOF), which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For ${}^{56,58}$Ti and ${}^{56-59}$V the mass uncertainties have been reduced down to the order of $10\mathrm{keV}$, shedding new light on the $N=34$ shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species ${}^{58}$Ti and ${}^{59}$V. With the new precision achieved, we reveal the non-existence of the $N=34$ empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied $\nu p_{3/2}$ orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the $\nu d_{5/2}$ and $\nu g_{9/2}$ orbits and compare the results with conventional shell model calculations, which exclude the $\nu g_{9/2}$ and the $\nu d_{5/2}$ orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at $N=34$.

References in corpus (20)

• Nuclear ground-state masses and deformations: FRDM(2012)
• Magic numbers in exotic nuclei and spin-isospin properties of {\it NN} interaction
• Novel features of nuclear forces and shell evolution in exotic nuclei
• Evolution of shell structure in exotic nuclei
• Thick-Restart Block Lanczos Method for Large-Scale Shell-Model Calculations
• Ab initio limits of atomic nuclei
• Novel shape evolution in exotic Ni isotopes and configuration-dependent shell structure
• Strong neutrino cooling by cycles of electron capture and ${\beta }^{-}$ decay in neutron star crusts
• Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K
• Dawning of the N=32 shell closure seen through precision mass measurements of neutron-rich titanium isotopes
• First direct mass measurements of nuclides around $Z=100$ with a Multireflection Time-of-Flight Mass Spectrograph
• Single-reference high-precision mass measurement with a multi-reflection time-of-flight mass spectrograph
• Precision Mass Measurement of ${}^{58-63}$Cr: Nuclear Collectivity towards the \emph{N}=40 Island of Inversion
• Shell evolution of $N=40$ isotones towards ${}^{60}$Ca: First spectroscopy of ${}^{62}$Ti
• Precision mass measurements of neutron-rich scandium isotopes refine the evolution of $N=32$ and $N=34$ shell closures
• Urca cooling pairs in the neutron star ocean and their effect on superbursts
• Nuclear Mass Measurements Map the Structure of Atomic Nuclei and Accreting Neutron Stars
• Wide-band mass measurements with a multi-reflection time-of-flight mass spectrograph
• Investigating nuclear structure near $N=32$ and $N=34$: Precision mass measurements of neutron-rich Ca, Ti and V isotopes
• First spectroscopy of 61Ti and the transition to the Island of Inversion at N = 40

Cited by in corpus (6)

• Improved description of nuclear charge radii: Global trends beyond $N=28$ shell closure
• Potential signature of new magicity from universal aspects of nuclear charge radii
• Prominent bump in the two-neutron separation energies of neutron-rich lanthanum isotopes revealed by high-precision mass spectrometry
• Universal Effective Charges in the $sd$ and $fp$ Shells
• Microscopic study of low-lying energy levels and electromagnetic properties in even-even ${}^{168-178}$Yb nuclei
• Evolution of shell structure at $\mathbf{N}=32$ and 34: Insights from realistic nuclear forces