Investigating the strength of the N = 34 subshell closure in 54Ca

D Steppenbeck ,H Baba ,Hiroshi Suzuki ,Takaharu Otsuka ,Yutaka Utsuno ,D Nishimura ,T Motobayashi ,Satoshi Takeuchi ,S Go ,N Fukuda ,H Sakuraï ,He Wang ,Michio Honma ,M Matsushita ,K Matsui ,S Michimasa ,Yoshinori Shiga ,P Doornenbal ,P.-A Söderström ,T Sumikama ,R Taniuchi ,N Aoi ,Jenny Lee ,J J Valiente-Dobón ,K Yoneda

doi:10.1088/1742-6596/445/1/012012

Abstract

Excited states in the exotic N = 34 isotope 54Ca have been measured for the first time via in-beam γ-ray spectroscopy with proton-knockout reactions from 55Sc and 56Ti radioactive beams on a Be reaction target at the Radioactive Isotope Beam Factory, Japan. A strong candidate for the transition from the first 2+ state to the 0+ ground state has been identified, in addition to several other weaker transitions. The structure of the N = 33 isotope 53Ca has also been investigated from the same data. Preliminary γ-ray energy spectra for 54Ca and 53Ca will be presented and the significance of the N = 34 subshell closure will be examined. Predictions of several shell-model interactions performed in the fp model space will be discussed in light of the new results.

Highlights

Over recent years, the evolution of nuclear shell structure in exotic, neutron-rich nuclei has attracted much attention on both the experimental and theoretical fronts
This observation led to a modified version of the GXPF1 Hamiltonian, labelled GXPF1A [14], in order to better reproduce the experimental systematics of the N ≈ 34 isotopes
The new interaction was found to show a systematic improvement in predictions of E(2+1 ) in the Cr isotopes, and the recent assignment of Jπ = 1/2− to the 55Ti ground state [15] supports the prediction of the GXPF1A interaction, indicating that the νf5/2 orbital lies above νp1/2 in Ti, albeit not high enough to result in a new subshell closure

Summary

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Introduction

Results and discussion