A First Glimpse at the Shell Structure beyond ${}^{54}$Ca: Spectroscopy of ${}^{55}$K, ${}^{55}$Ca, and ${}^{57}$Ca

Abstract

States in the $N=35$ and 37 isotopes ${}^{55,57}$Ca have been populated by direct proton-induced nucleon removal reactions from ${}^{56,58}$Sc and ${}^{56}$Ca beams at the RIBF. In addition, the $(p,2p)$ quasi-free single-proton removal reaction from ${}^{56}$Ca was studied. Excited states in ${}^{55}$K, ${}^{55}$Ca, and ${}^{57}$Ca were established for the first time via in-beam $\gamma$-ray spectroscopy. Results for the proton and neutron removal reactions from ${}^{56}$Ca to states in ${}^{55}$K and ${}^{55}$Ca for the level energies, excited state lifetimes, and exclusive cross sections agree well with state-of-the-art theoretical calculations using different approaches. The observation of a short-lived state in ${}^{57}$Ca suggests a transition in the calcium isotopic chain from single-particle dominated states at $N=35$ to collective excitations at $N=37$.

arXiv commentaccepted Phys. Lett. B

References in corpus (24)

• Improved nuclear matter calculations from chiral low-momentum interactions
• Accurate nuclear radii and binding energies from a chiral interaction
• Evolution of shell structure in exotic nuclei
• Shell model study of the isobaric chains A=50, A=51 and A=52
• Thick-Restart Block Lanczos Method for Large-Scale Shell-Model Calculations
• A nucleus-dependent valence-space approach to nuclear structure
• Non-Empirical Interactions for the Nuclear Shell Model: An Update
• Identification and Separation of Radioactive Isotope Beams by the BigRIPS Separator at the RIKEN RI Beam Factory
• Structure of the lightest tin isotopes
• Ab initio limits of atomic nuclei
• Shape transitions in exotic Si and S isotopes and tensor-force-driven Jahn-Teller effect
• A consistent analysis of (e,e'p) and (d,3He) experiments
• Saturation with chiral interactions and consequences for finite nuclei
• Novel chiral Hamiltonian and observables in light and medium-mass nuclei
• DALI2: A NaI(Tl) detector array for measurements of $\gamma$ rays from fast nuclei
• The Magnus expansion and the in-medium similarity renormalization group
• Ab-initio self-consistent Gorkov-Green's function calculations of semi-magic nuclei - I. Formalism at second order with a two-nucleon interaction
• Quenching of single-particle strength from direct reactions with stable and rare-isotope beams
• Ab-initio self-consistent Gorkov-Green's function calculations of semi-magic nuclei - II. Numerical implementation at second order with a two-nucleon interaction
• Self-consistent Green's function theory for atomic nuclei
• Spins and Magnetic Moments of ${}^{49}$K and ${}^{51}$K: establishing the 1/2${}^{+}$ and 3/2${}^{+}$ level ordering beyond $N$ = 28
• Mass-number and isotope dependence of the local microscopic optical potential for polarized proton scattering
• Moving away from singly-magic nuclei with Gorkov Green's function theory
• Isomeric states in neutron-rich nuclei around $N=40$

Cited by in corpus (4)

• Spectroscopy of deeply bound orbitals in neutron-rich Ca isotopes
• Universal Effective Charges in the $sd$ and $fp$ Shells
• Spectroscopy of ${}^{52}$K
• Systematic analysis of the nuclear absorption effect on the cross section of the knockout reaction