Ground-state β-decay spectroscopy of Ta 187

Beta-decay spectroscopy of the Ta187 ground state was performed at the KEK Isotope Separation System. β-delayed γ rays corresponding to the previously reported in-beam transitions were observed. The β-decay half-life of the Ta187 ground state was determined to be 283(10) s by analyzing a time spectrum of β-γ coincidence events. The β-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 Iπ=7/2+ originating from the odd-proton orbit π7/2[404] were assigned with high confidence, which is consistent with the systematics of neighboring odd-A nuclides.