Precise absolute $\gamma$-ray and ${\beta }^{-}$-decay branching intensities in the decay of ${}_{29}{}^{67}\mathrm{Cu}$

Absolute $\gamma$-ray emission probabilities in the ${\beta }^{-}$ decay of ${}^{67}\mathrm{Cu}$ were measured by means of $\gamma$-ray and ${\beta }^{-}$-decay singles and ${\beta }^{-}\text{−}\gamma$ coincidences. The new results, together with the known decay scheme of ${}^{67}\mathrm{Cu}$, were used to determine absolute ${\beta }^{-}$-decay branching intensities. The present data differ significantly from previously published values. In addition, the half-life of the $I^{\pi }={\frac{1}{2}}^{-}$ isomer in ${}^{67}\mathrm{Zn}$ was measured as $T_{1/2}=9.37\left(4\right) \mu \mathrm{s}$, in a good agreement with earlier measurements. From the analysis of the Fermi–Kurie plots, $Q_{{\beta }^{-}}\left(\text{g.s.}\right)=560.3\left(10\right)$ keV was deduced, which differs from the previously measured value of 577(8) keV but is in good agreement with $Q_{{\beta }^{-}}\left(\text{g.s.}\right)=561.3(15)$ keV recommended in the latest Atomic Mass Evaluation.

Figure 1

Decay scheme of ${}^{67}\mathrm{Cu}$ [4]. The $\gamma$-ray energies and the half-life of the $I^{\pi }={\frac{1}{2}}^{-}$ level shown the are from the present work.

Figure 2

$\gamma$-ray singles spectrum of the open ${}^{67}\mathrm{Cu}$ source measured with the LEPS. The $\gamma$ rays are labeled with their rounded-off energies in keV. The low-energy 8.6 and 9.6 keV peaks correspond to the $K_{\alpha }$ and $K_{\beta }$ Zn x-rays, respectively.

Figure 3

Electron (${\beta }^{-}$ and conversion electrons) singles spectrum of the ${}^{67}\mathrm{Cu}$ open source measured with the 25-${\mathrm{mm}}^2-\mathrm{area}\times 500\text{−}\mu \mathrm{m}$-thick PIPS detector. The $K$ and $L$ conversion electron peaks associated with the 91.4, 93.4, and 184.6 keV $\gamma$ rays are labeled with their energies in keV.

Figure 4

${\beta }^{-}$ spectra of the ${}^{67}\mathrm{Cu}$ open source measured with the 150-${\mathrm{mm}}^2\text{−}\mathrm{area}\times 1$-mm-thick PIPS detector. The top one is a ${\beta }^{-}$ singles spectrum with contributions from room background and conversion electrons subtracted, while the bottom one is a ${\beta }^{-}\text{−}\gamma$ coincidence spectrum produced by gating on the 185 keV $\gamma$ ray.

Figure 5

Time spectrum used to determine the half-life of the $I^{\pi }={\frac{1}{2}}^{-}$ isomer in ${}^{67}\mathrm{Zn}$. The solid line corresponds to a least-squares fit to the data with a single-exponential decay and a constant background (shown as the dashed line).