$\beta$-decay half-lives of ${}^{134,134m}\mathrm{Sb}$ and their isomeric yield ratio produced by the spontaneous fission of ${}^{252}\mathrm{Cf}$

A number of fission products possess isomeric states which have a nuclear spin significantly different from that of the ground state. The yield ratio of these states following fission is influenced by the angular momentum present in the fissioning system. The ${}^{134m,134}\mathrm{Sb}$ yield ratio had not been previously measured in the spontaneous fission of ${}^{252}\mathrm{Cf}$; however, it had previously been observed to favor the ($7^{-}$) isomer over the ($0^{-}$) ground state in ${}^{235}\mathrm{U}(n_{th},f$) and ${}^{232}\mathrm{Th}$(25 MeV $p,f$). Using a mass-separated beam of low-energy ${}^{134,134m}\mathrm{Sb}$ ions produced by ${}^{252}\mathrm{Cf}$ spontaneous fission at the CARIBU facility, $\beta$ particles and $\gamma$ rays were detected using the SATURN/X-Array decay station to determine the fission-yield ratio and $\beta$-decay half-lives. The ${}^{134m}\mathrm{Sb}$ to ${}^{134}\mathrm{Sb}$ fission yield was determined to be $2.03\pm 0.05$ and the half-lives of ${}^{134m}\mathrm{Sb}$ and ${}^{134}\mathrm{Sb}$ were found to be $9.87\pm 0.08$ s and $0.674\pm 0.004$ s, respectively. These results represent the first isomeric yield ratio measurement for this nucleus, and improved measurements of the ${}^{134}\mathrm{Sb}$ ground state and the ${}^{134m}\mathrm{Sb}$ isomer half-lives.

Figure 1

The $\gamma$-ray energy spectrum, with constant background lines subtracted, of the $\beta$-gated $\gamma$-ray coincidences in the long tape cycle with the 297-, 706-, and 1279-keV $\gamma$ rays.

Figure 2

The time dependence of the build up and decay of the $\beta$-gated $\gamma$ counts during the long tape cycle for (a) 297-keV, (b) 706-keV, and (c) 1279-keV $\gamma$ rays.

Figure 3

The $\beta$-singles counts collected during the (a) short and (b) long tape-cycle time (black) compared to fit results (red solid line) which include contributions from the decays of ${}^{134}\mathrm{Sb}$ (blue or dark dashed line), ${}^{134m}\mathrm{Sb}$ (green or light dashed line), and backgrounds from the room and ${}^{134}\mathrm{Te}$ build up (gray wide dashed line).