High-spin states inCe127andCe129: Further evidence for triaxial nuclear shapes

Abstract

High-spin states have been studied in the neutron-deficient odd-$N$ $^{127}\mathrm{Ce}$ and $^{129}\mathrm{Ce}$ isotopes, produced in $^{100}\mathrm{Mo}$($^{32}\mathrm{S}$,$5n\ensuremath{\gamma}$) and $^{100}\mathrm{Mo}$($^{34}\mathrm{S}$,$5n\ensuremath{\gamma}$) reactions, using the Euroball and Eurogam $\ensuremath{\gamma}$-ray spectrometers, respectively. A quadruples analysis (${\ensuremath{\gamma}}^{4}$) of the coincident $\ensuremath{\gamma}$-ray data has established new band structures in $^{127,129}\mathrm{Ce}$ and extended the known bands to higher spin. In addition, links have been established between two positive-parity bands in $^{127}\mathrm{Ce}$ allowing a reassignment of ${I}^{\ensuremath{\pi}}=1/{2}^{+}$ to the ground state of this nucleus. Configuration assignments are made by comparison of band properties with cranked Woods-Saxon calculations and systematics of other light odd-$N$ cerium isotopes. Unusually large signature splitting in the negative-parity bands is discussed in terms of nonaxial nuclear shapes induced by the core-polarization effects of ${h}_{11/2}$ neutrons.