Large-amplitude dynamics of axial and triaxial quadrupole deformation in ${}^{24,26}\mathrm{Mg}$, ${}^{24}\mathrm{Ne}$, and ${}^{28}\mathrm{Si}$ is investigated on the basis of the quadrupole collective Hamiltonian constructed with the use of the constrained Hartree-Fock-Bogoliubov plus the local quasiparticle random-phase approximation method. The calculation reproduces well properties of the ground rotational bands, and $\beta$ and $\gamma$ vibrations in ${}^{24}\mathrm{Mg}$ and ${}^{28}\mathrm{Si}$. The $\gamma$ softness in the collective states of ${}^{26}\mathrm{Mg}$ and ${}^{24}\mathrm{Ne}$ are discussed. Contributions of the neutrons and protons to the transition properties are also analyzed in connection with the large-amplitude quadrupole dynamics.

• Received 26 August 2010

DOI:https://doi.org/10.1103/PhysRevC.83.014321