Identification of a nanosecond isomer of $$^{164}$$Tb

Abstract

Abstract This letter reports on the identification of a new isomeric state of $$^{164}$$ 164 Tb ( $$Z=65$$ Z = 65 , $$N=99$$ N = 99 ), which was measured with the DESPEC setup at the GSI Helmholtzzentrum für Schwerionenforschung GmbH following the first relativistic fragmentation of an $$^{170}$$ 170 Er primary beam. From the time distribution and coincidences of the emitted $$\gamma $$ γ rays, the isomer is tentatively assigned to a state with spin-parity $$(7^{-})$$ ( 7 - ) at an excitation energy of $$283.3(2)~\textrm{keV}$$ 283.3 ( 2 ) keV with a half-life of $$159(11)~\textrm{ns}$$ 159 ( 11 ) ns . The isomer is interpreted as the $$\pi 7/2^{-}[523]\otimes \nu 7/2^{+}[633]$$ π 7 / 2 - [ 523 ] ⊗ ν 7 / 2 + [ 633 ] configuration from the Nilsson orbital systematics. These results represent the first report of $$\gamma $$ γ -ray spectroscopy of $$^{164}$$ 164 Tb, providing insight into the ground-state and low-lying level structure.