${\beta }^{-}$ decay study of the ${}^{66}$Mn - ${}^{66}$Fe - ${}^{66}$Co - ${}^{66}$Ni chain

Abstract

Background: Shell evolution can impact the structure of the nuclei and lead to effects such as shape coexistence. The nuclei around ${}^{68}$Ni represent an excellent study case, however, spectroscopic information of the neutron-rich, $Z<28$ nuclei is limited. Purpose: The goal is to measure $\gamma$-ray transitions in ${}^{66}$Fe, ${}^{66}$Co and ${}^{66}$Ni populated in the ${\beta }^{-}$ decay of ${}^{66}$Mn, to determine absolute $\beta$-feedings and relative $\gamma$-decay probabilities and to compare the results with Monte Carlo Shell Model calculations in order to study the influence of the relevant single neutron and proton orbitals occupancies around $Z=28$ and $N=40$. Method: The low-energy structures of ${}^{65,66}$Fe, ${}^{66}$Co and ${}^{66}$Ni were studied in the ${\beta }^{-}$ decay of ${}^{66}$Mn produced at ISOLDE, CERN. The beam was purified by means of laser resonance ionization and mass separation. The $\beta$ and $\gamma$ events detected by three plastic scintillators and two MiniBall cluster germanium detectors, respectively, were correlated in time to build the low-energy excitation schemes and to determine the $\beta$-decay half-lives of the nuclei. Results: The relative small $\beta$-decay ground state feeding of ${}^{66}$Fe obtained in this work is at variant to the earlier studies. Spin and parity $1^{+}$ was assigned to the ${}^{66}$Co ground state based on the strong ground state feeding in the decay of ${}^{66}$Fe as well as in the decay of ${}^{66}$Co. Experimental log(ft) values, $\gamma$-ray deexcitation patterns and energies of excited states were compared to Monte Carlo Shell Model calculations. Based on this comparison, spin and parity assignments for the selected number of low-lying states in the ${}^{66}$Mn to ${}^{66}$Ni chain were proposed. Conclusions: The $\beta$-decay chain starting ${}^{66}$Mn towards ${}^{66}$Ni, crossing $N=40$, evolves from deformed nuclei to sphericity...

accepted for publication in PRC

References in corpus (7)

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Cited by in corpus (2)

• Shape Coexistence at Zero Spin in 64Ni Driven by the Monopole Tensor Interaction
• Detailed low-spin spectroscopy of 65Ni via neutron capture reaction