Large-amplitudeQn-Qpcollectivity in the neutron-rich oxygen isotopeO20

By means of HFB calculations with independent constraints on axial neutron and proton quadrupole moments ${\widehat{Q}}_n$ and ${\widehat{Q}}_p$, we investigate the large amplitude isoscalar and isovector deformation properties of the neutron-rich isotope ${}^{20}\mathrm{O}$. Using the particle-number and angular-momentum projected generator coordinate method, we analyze the collective dynamics in the $\{\langle {\widehat{Q}}_n\rangle ,\langle {\widehat{Q}}_p\rangle \}$ plane. The parametrization SLy4 of the Skyrme interaction is used for all calculations in connection with a density-dependent zero-range pairing interaction. Our results show that already for this moderately neutron-rich nucleus the transition moments are modified when independent neutron and proton collective dynamics are allowed.