Identification of the 21,ms+ mixed-symmetry state in 136Ce.

The evolution of the one-quadrupole phonon mixed-symmetry state is important for understanding the role of the quadrupole proton-neutron interaction in the valence shell. To study the evolution of the 21,ms+ mixed-symmetry state in the N = 78 isotones above Z = 50, a Coulomb excitation measurement was performed to identify the 21,ms+ state in 136Ce by measuring absolute transition strengths. The 21,ms+ state was found to be predominantly concentrated in the 24+ state of this nucleus. The simple picture of shell stabilization given to account for the fragmentation of the strength observed in 138Ce does not seem to apply to 136Ce. [ABSTRACT FROM AUTHOR]