Hexadecapole degree of freedom in 94Mo

The weakly collective nucleus 94Mo has been considered an excellent example of quadrupole vibrational mixed-symmetry structure. Algebraic models such as the interacting boson model-2 have been largely unsuccessful in describing the structure of the 42+ state, due to the strong M1 transition between the 42+ and 41+ states, and the low energy of the 42+ state. In this Letter, we show that introducing g-bosons into the interacting boson model-2 allows for the first time a description of the electromagnetic decay properties of the low-lying 4+ states in 94Mo within an algebraic model. The hexadecapole degree of freedom is shown to be important for the description of the collective low-energy structure of nuclei in this region.