Radioactive decay of 80Y and low-lying states in 80Sr

The β+/EC decay of a mass-separated 80Y source has been studied by β- and γ-ray spectroscopy following the bombardment of a thin 24Mg target with 58Ni ions at 190 MeV. An extended decay scheme with 14 new states in 80Sr 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 80Sr can also be grouped into a γ-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 80Yβ-decay fragmentation and log ft values have also been used to assign spin and parity of 4- and 1- to the parent ground state and the 228.5 keV isomeric state, respectively. copyright 1999 The American Physical Society