Isomeric and $\ensuremath{\beta}$-decay spectroscopy of $^{173,174}\mathrm{Ho}$

Isomeric and $β$ -decay spectroscopy of ${}^{173, 174}{Ho}$

J. J. Liu et al.

Phys. Rev. C 102, 024301 – Published 3 August 2020

Abstract

$β$ -decay spectroscopy of ${}^{173, 174}{Ho}$ ( $Z$ $=$ 67, $N$ $=$ 106,107) was conducted at Radioactive Isotope Beam Factory at RIKEN by using in-flight fission of a 345-MeV/u ${}^{238}U$ primary beam. A previously unreported isomeric state at 405 keV with half-life of 3.7(12) $μ s$ and a spin and parity of ( $3 / 2^{+}$ ) is identified in ${}^{173}{Ho}$ . Moreover, a new state with a spin and parity of $9^{-}$ was discovered in ${}^{174}{Er}$ . The experimental log ft values of 5.84(20) and 5.25(18) suggest an allowed-hindered $β$ decay from the ground state of ${}^{174}{Ho}$ to the $K^{π} = 8^{-}$ isomeric state in ${}^{174}{Er}$ . Configuration-constrained potential energy surface (PES) calculations were performed and the predictions are in reasonable agreement with the experimental results.

Received 11 October 2019
Accepted 2 July 2020

DOI:https://doi.org/10.1103/PhysRevC.102.024301

Physics Subject Headings (PhySH)

Beta decay Electromagnetic transitions Isomer decays Nuclear structure & decays

150 ≤ A ≤ 189

Radioactive beams

Nuclear Physics

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Vol. 102, Iss. 2 — August 2020

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Figure 1
(a) $β − γ$ spectra with gate on $β$ -decay events within a time window (T) of 10 s after implantation of ${}^{174}{Ho}$ . (b) DSSD spectrum measured with a sum gate of $2^{+} \to 0^{+}$ , $4^{+} \to 2^{+}$ , $6^{+} \to 4^{+}$ , $8^{+} \to 6^{+}$ , and $8^{-} \to 8^{+}$ decay transitions in ${}^{174}{Er}$ . Energies marked in (b) were theoretical energies from the BrIcc model [14]. The corresponding $γ$ transitions and types of IC electrons are shown in the brackets. (c) and (d) $β − γ$ spectra with gates and different electron energies ( $E_{e}$ ). (e) Total decay curve of ${}^{174}{Ho}$ and associated fit based on decay chain of ${}^{174}{Ho} \to {}^{174 m}{Er} \to {}^{174}{Er} \to {}^{174 m}{Tm} \to {}^{174}{Tm} \to {}^{174}{Yb}$ . Total fit (red), parent component ${}^{174}{Ho}$ (black), daughter component ${}^{174 m}{Er}$ (green), and background (brown) are shown in solid line. The other decay components ${}^{174}{Er} {}^{174 m}{Tm}$ and ${}^{174}{Tm}$ are shown in dot-dash line in total. (f) and (g) Time distribution of pure $β$ -decay events ( $E_{DSSD} \geq$ 300 keV) and low internal conversion electron events ( $E_{DSSD} \leq 100$ keV). (h) and (i) Time profiles of gating $γ$ energy 199-keV transition and sum of isomeric transition.
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Figure 2
Systematic study of $N =$ 106 isotones near ${}^{174}{Er}$ , including ${}^{172}{Dy}$ [25], ${}^{176}{Yb}$ [17], ${}^{178}{Hf}$ [18], ${}^{180}W$ [19], and ${}^{182}{Os}$ [20]. Similar energy transitions are found above $8^{-}$ isomeric states of ${}^{176}{Yb}$ to ${}^{178}{Hf}$ .
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Figure 3
$β$ -decay scheme of ${}^{174}{Ho}$ proposed from this experiment. Apparent beta feedings $I_{β}$ and the corresponding log ft values are given on the left-hand side of the level scheme. The states and transitions marked in red are previously unreported. Other black $γ$ transitions were previously reported in Ref. [15].
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Figure 4
Schematic diagrams of two-quasiparticle configurations of ${}^{174}{Ho}$ and ${}^{174}{Er}$ . The solid and dash lines are the Nillson orbitals with positive and negative parities, respectively. The red and blue dots are protons and neutrons. The bold black arrow represents the $β$ -decay path in ${}^{174}{Ho} \to {}^{174}{Er}$ .
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Figure 5
(a) Delayed $γ$ spectrum with gate on 2 $μ s$ after ${}^{173}{Ho}$ implantation. (b) $β − γ$ spectra measured with 5-s time difference between implantation and $β$ events. The time window for $β$ and $γ$ is with $2 μ s$ . Energy peaks marked in red are newly discovered $γ$ transitions in $β$ decay of ${}^{173}{Ho}$ to ${}^{173}{Er}$ . (c) Time distribution of 405 keV after implantation of ${}^{173}{Ho}$ . (d) Total $β$ curve of ${}^{173}{Ho}$ and associated fit based on decay of ${}^{173}{Ho} \to {}^{173}{Er} \to {}^{173 m}{Tm} \to {}^{173}{Tm} \to {}^{173}{Yb}$ . Total fit (red), parent component ${}^{173}{Ho}$ (black), and background (brown) are shown in solid line. The decay components of ${}^{173}{Er}$ and ${}^{173}{Tm}$ are shown in dash-solid line in green.
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Physical Review C

covering nuclear physics

Isomeric and $β$ -decay spectroscopy of ${}^{173, 174}{Ho}$

J. J. Liu et al.

Phys. Rev. C 102, 024301 – Published 3 August 2020

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Physical Review C

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Isomeric and β-decay spectroscopy of Ho173,174

J. J. Liu et al.

Phys. Rev. C 102, 024301 – Published 3 August 2020

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Isomeric and $β$ -decay spectroscopy of ${}^{173, 174}{Ho}$