Ground-state β -decay spectroscopy of Ta187

Abstract

Beta-decay spectroscopy of the $^{187}\mathrm{Ta}$ ground state was performed at the KEK Isotope Separation System. $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays corresponding to the previously reported in-beam transitions were observed. The $\ensuremath{\beta}$-decay half-life of the $^{187}\mathrm{Ta}$ ground state was determined to be 283(10) s by analyzing a time spectrum of $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidence events. The $\ensuremath{\beta}$-decay branching ratio and log($ft$) values were evaluated for the first time. Based on the newly evaluated log($ft$) values of $>6.0$ and a decay scheme, spin-parity values of ${I}^{\ensuremath{\pi}}=7/{2}^{+}$ originating from the odd-proton orbit $\ensuremath{\pi}7/2[404]$ were assigned with high confidence, which is consistent with the systematics of neighboring odd-$A$ nuclides.