The decays of $T_z=1/2\mathrm{}$ series nuclei ${}^{81}\mathrm{Zr}$ and ${}^{85}\mathrm{Mo}$ have been restudied via their $\beta$-delayed proton decay by using p-$\gamma$ coincidence measurements. The $\beta$-delayed proton spectra populating the first excited states of the final nuclei have been obtained. By using statistical model calculations with level densities calculated with a backshifted Fermi gas model, the spin and parity for the ground state of ${}^{81}\mathrm{Zr}$ have been tentatively assigned to be ${3/2}^{-}$ and those for ${}^{85}\mathrm{Mo}$ to be ${1/2}^{-}.$ Their $Q_{\mathrm{e}.\mathrm{c}.\mathrm{}}-B_p$ values are $4.7\pm 0.2$ and $5.1\pm 0.2\hspace{0.5em}\mathrm{MeV},$ which correspond to mass excesses of $-58.3\pm 0.2\hspace{0.5em}\mathrm{MeV}$ for ${}^{81}\mathrm{Zr}$ and of $-59.1\pm 0.4\hspace{0.5em}\mathrm{MeV}$ for ${}^{85}\mathrm{Mo},$ respectively. Combining the measured half-lives with the calculated partial ones yields branches of $\beta$-delayed proton decay for ${}^{81}\mathrm{Zr}$ and ${}^{85}\mathrm{Mo}$ of $(1.2\mathrm{}\pm 0.2)\times {10}^{-3}$ and $(1.4\mathrm{}\pm 0.2)\times {10}^{-3},$ respectively.

• Received 14 April 1998

DOI:https://doi.org/10.1103/PhysRevC.59.2402