The hexadecapole degree of freedom in rotational nuclei

We present a new description of the hexadecapole degree of freedom in nuclei in the framework of the Interacting Boson Model, by the addition of a g boson. Results of this model are presented concerning E2 transitions in ¹⁵⁶Gd. Also, the problem of the importance of the L = 4 degree of freedom in the low-lying collective spectrum of rotational nuclei is studied.