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 0_5^+ state exhibits decay properties which more closely align with those predicted for a spherical shape, while the 0_4^+ level is suggested to be associated with a weakly-deformed shape similar to one related to the 0_2^+ state.