Determination of the spins and parities for the 0⁺₄ and 0⁺₅ states in ¹⁰⁰Zr

Two 0⁺ states at 1294.5 and 1774.0 keV, together with three 2⁺ and one 4⁺ levels, were identified or unambiguously spin-parity assigned for the first time in ¹⁰⁰Zr utilizing γ-ray spectroscopy and γ-γ angular correlation techniques with the Gammasphere spectrometer, following the β⁻ decay of neutron-rich, mass separated 100,100mY isotopes. Comparisons with recent Monte Carlo Shell-Model (MCSM) calculations indicate that these two states are candidates for the bandhead of a sequence in a shape-coexisting spherical minimum predicted to be located around ≈1500 keV. According to the measured relative B(E2)ᵣₑₗₐₜᵢᵥₑ transition probabilities, the 0₅⁺ state exhibits decay properties which more closely align with those predicted for a spherical shape, while the 0₄⁺ level is suggested to be associated with a weakly-deformed shape similar to one related to the 0₂⁺ state.