β-delayed proton decays of theTz=1/2series nuclei,81Zrand85Mo

Abstract

The decays of ${T}_{z}=1/2$ series nuclei ${}^{81}\mathrm{Zr}$ and ${}^{85}\mathrm{Mo}$ have been restudied via their $\ensuremath{\beta}$-delayed proton decay by using p-$\ensuremath{\gamma}$ coincidence measurements. The $\ensuremath{\beta}$-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 ${3/2}^{\ensuremath{-}}$ and those for ${}^{85}\mathrm{Mo}$ to be ${1/2}^{\ensuremath{-}}.$ Their ${Q}_{\mathrm{e}.\mathrm{c}.}\ensuremath{-}{B}_{p}$ values are $4.7\ifmmode\pm\else\textpm\fi{}0.2$ and $5.1\ifmmode\pm\else\textpm\fi{}0.2 \mathrm{MeV},$ which correspond to mass excesses of $\ensuremath{-}58.3\ifmmode\pm\else\textpm\fi{}0.2 \mathrm{MeV}$ for ${}^{81}\mathrm{Zr}$ and of $\ensuremath{-}59.1\ifmmode\pm\else\textpm\fi{}0.4 \mathrm{MeV}$ for ${}^{85}\mathrm{Mo},$ respectively. Combining the measured half-lives with the calculated partial ones yields branches of $\ensuremath{\beta}$-delayed proton decay for ${}^{81}\mathrm{Zr}$ and ${}^{85}\mathrm{Mo}$ of $(1.2\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $(1.4\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3},$ respectively.