Radioactive decay of80Yand low-lying states in80Sr

Abstract

The ${\ensuremath{\beta}}^{+}/\mathrm{EC}$ decay of a mass-separated ${}^{80}\mathrm{Y}$ source has been studied by $\ensuremath{\beta}$- and $\ensuremath{\gamma}$-ray spectroscopy following the bombardment of a thin ${}^{24}\mathrm{Mg}$ target with ${}^{58}\mathrm{Ni}$ ions at 190 MeV. An extended decay scheme with 14 new states in ${}^{80}\mathrm{Sr}$ has been identified including the first observation of negative-parity states. The low-lying positive-parity states have been found to be clustered indicating a pattern of one-, two-, and possibly three-phonon multiplets characteristic of an anharmonic vibrator. Some states in ${}^{80}\mathrm{Sr}$ can also be grouped into a $\ensuremath{\gamma}$-vibrational band. In general the low-lying states in light strontium isotopes show vibrationlike collectivity which evolves to rotational behavior with increasing spin and decreasing neutron number. The observed ${}^{80}\mathrm{Y}\ensuremath{\beta}$-decay fragmentation and $\mathrm{log}\mathrm{ft}$ values have also been used to assign spin and parity of ${4}^{\ensuremath{-}}$ and ${1}^{\ensuremath{-}}$ to the parent ground state and the 228.5 keV isomeric state, respectively.