Determination of the spins and parities for the 0${}_4^{+}$ and 0${}_5^{+}$ states in ${}^{100}$Zr

Abstract

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 ${}^{100}$Zr utilizing ${\hat{I}}^3$-ray spectroscopy and ${\hat{I}}^3$-${\hat{I}}^3$ angular correlation techniques with the Gammasphere spectrometer, following the $β^{-}$ decay of neutron-rich, mass separated ${}^{100,100m}$Y 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 $\approx$1500 keV. According to the measured relative B(E2)${}_{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.