The $\gamma$-deformation and $\gamma$-softness.

Depending on the $\beta_2$ and $\gamma$ parameters, deformed nuclei can be subdivided into prolate, oblate and triaxial deformed nuclei. In the current work, when shape calculations are presented, $\gamma$=0$^o$ and $\gamma$=60$^o$ correspond to axially symmetric prolate (cigar shape) and oblate (disk shape), respectively, with 0 $^o <\gamma <$60$^o$ indicating triaxial shapes (see figure ). In this description, axial symmetry at $\gamma$=0$^o$ is equivalent to $\gamma$=-120$^o$. Hence, the sector between 0$^o$ and 60$^o$ contains all shapes uniquely and is taken as the representative one [6].

Figure: The prolate and oblate axes for deformed nuclei and the unique region which contains all shapes uniquely.

The nucleus is defined as being `soft' with respect to the $\gamma$ degree of freedom when a range of possible shapes are allowed within a relatively small excitation energy. This feature will be referred to as $\gamma$-softness of the nuclear state. In this case, the nucleus is sensitive to the shape-polarizing effects of specific multi-quasiparticle configurations and the nuclear shape may drive from prolate to oblate or viceversa.