Half-life measurement of the107-keV isomeric state in 45Cr

ORAL

Abstract

The atomic nuclei near the self-conjugate line at Z=21 or N=21 are known to systematically have spin-gap isomers formed by low-lying d3/2 and f7/2 orbitals. In 42-47Sc isotopes, isomers with the d3/2-hole configuration have already been reported, while some of the mirror configuration isomers within the N=21 isotones remain unreported.

Our presentation will report an isomeric state in 45Cr with an excitation energy of 107 keV. In the previous studies, this state was tentatively assigned as the mirror state of a known isomeric state at 12.4 keV in 45Sc with a half-life of 325.8 ms. Only the lower limit of the lifetime of the 107-keV state was reported before (>80 us [Uthayakumaar et al. PRC106, 024327]), and it was estimated to be on the order of 100 micro-seconds. Our recent experiment successfully determined the lifetime of this state for the first time.

We carried out the delayed gamma-ray spectroscopy of 45Cr in combination with the TOF-Bρ direct mass measurements at OEDO-SHARAQ in RIBF. After the TOF measurements of the secondary beam particles, they were implanted into an active stopper consisting of two plastic scintillators located downstream of the final focal plane of OEDO-SHARAQ. For the delayed gamma-ray spectroscopy, two HPGe detectors were placed in the proximity of the active stopper, perpendicular to the beamline.

In this presentation, we will discuss the features of the isomeric state in 45Cr and 45Sc and the isospin symmetry of pf shell nuclei in comparison with the theoretical predictions.

*This work was partly supported by JSPS KAKENHI Grant Number JP22H01230.

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Presenters

  • Mei Amitani

    • Tokyo City University

Authors

  • Mei Amitani

    • Tokyo City University

  • Yuki Nakamura

    • Tokyo City University

  • Chihaya Fukushima

    • Tokyo City University

  • Daiki Nishimura

    • Tokyo City University
    • Tokyo city University
    • Tokyo City Univ.

  • Shin'ichiro Michimasa

    • CNS, The University of Tokyo
    • The University of Tokyo
    • Center for Nuclear Study, the University of Tokyo
    • Center for Nuclear Study, The University of Tokyo
    • CNS, University of Tokyo
    • CNS, University of Tokyo, Japan

  • Shutaro Hanai

    • Center for Nuclear Study, the University of Tokyo
    • Center for Nuclear Study, The University of Tokyo

  • Eiji Ideguchi

    • RCNP, Osaka University

  • Nobuaki Imai

    • Center for Nuclear Study, the University of Tokyo
    • Center for Nuclear Study, The University of Tokyo
    • CNS, University of Tokyo
    • CNS, University of Tokyo, Japan
    • Center for Nuclear Study, University of Tokyo

  • Keita Kawata

    • Center for Nuclear Study, the University of Tokyo
    • Research Center for Nuclear Physics,Osaka University

  • Hiroki Nishibata

    • Kyushu University

  • Kodai Okawa

    • Center for Nuclear Study, the University of Tokyo

  • Takeshi Y Saito

    • Center for Nuclear Study, the University of Tokyo, RIKEN AMO physics Laboratory
    • RIKEN AMO Physics Laboratory, Center for Nuclear Study, the University of Tokyo
    • Atomic, Molecular, and Optical Physics Laboratory, RIKEN

  • Daisuke Suzuki

    • RIKEN Nishina Center

  • Hiroyuki Takahashi

    • Tokyo City University

  • Hisato Tanaka

    • Kyushu University

  • Rin Yokoyama

    • CNS, The University of Tokyo
    • Center for Nuclear Study, the University of Tokyo