Influence of a strong proton-neutron interaction on mass 100 nuclei and properties of the octupole two-phonon multiplet in96Zr

Experimental evidence, which suggests a strong proton-neutron interaction giving rise to deformation and influencing the deformation properties of mass 100 nuclei, is reviewed, as is the large variation in the interaction strength for N=59 isotones and for coexisting states of 46≤Z≤54 isotones. Properties of the recently discovered octupole two-phonon multiplet in⁹⁶Zr are presented, compared to spdf-boson IBM calculations, and consequences of its fragmentation are discussed.