Evidence of oblate-prolate shape coexistence in the strongly-deformed nucleus Cs
K.K. Zheng (Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France, Key Laboratory of High Precision Nuclear Spectroscopy, Center for Nuclear Matter Science, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China); C.M. Petrache (Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France)
; Z.H. Zhang (Mathematics and Physics Department, North China Electric Power University, Beijing, China); P.W. Zhao (State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing, China); Y.K. Wang (State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing, China); et al - Show all 36 authors
Prolate-oblate shape coexistence close to the ground state in the strongly-deformed proton-rich nuclei is reported for the first time. One of the four reported bands in $^{119}$Cs, built on a state at 670 keV, consists of nearly degenerate signature partners, and has properties which unequivocally indicate the strongly-coupled configuration associated with oblate shape. Together with the decoupled band built on the prolate state at 110 keV, for which a half-life of has been measured, the new bands bring evidence of shape coexistence at low spin in the proton-rich strongly deformed nuclei, a phenomenon predicted since long time, but not yet observed. Calculations using the particle-number conserving cranked shell model and two dimensional tilted axis cranking covariant density functional theory support and well reproduce the observed oblate and prolate coexisting low-energy states in $^{119}$Cs.