We studied in a microscopic multiphonon approach the proton-neutron symmetry and phonon structure of some low-lying states recently discovered in ${}^{92}\mathrm{Zr}$. We confirm the breaking of $F$-spin symmetry, but argue that the breaking mechanism is more complex than the one suggested in the original shell model analysis of the data. We found other new intriguing features of the spectrum, such as a pronounced multiphonon fragmentation of the states and a tentative evidence of a three-phonon mixed-symmetry state.

• Received 9 January 2004

DOI:https://doi.org/10.1103/PhysRevC.69.044312