Shell-model search for the mixed-symmetry 2+ state in sd-shell nuclei and core-polarization E2 charges

The proton-neutron interacting boson model (IBM-2) which distinguishes proton and neutron degrees of freedom has predicted mixed symmetry state in a low excitation energy region. The symmetry property is characterized by F-spin. The mixed symmetry 1+ state has been observed in a number of nuclei, however, the existence of the IBM-2 mixed symmetry 2+ state has not been confirmed. Motivated by the shell model study for fp-shell nuclei, a systematic shell model search has been performed for the mixed symmetry 2+ state in the sd-shell region. The shell model calculation was made for even-even nuclei in the full configuration with the effective interaction of Wildenthal. The E2 and M1 transitions were taken as the measure in the search for the mixed symmetry 2+ state. The shell model prediction was compared with the experimental data. The shell model predicted a candidate in S-34, the second 2+ state, which has strong isovector-dominant E2 and M1 strengths. The mixed symmetry 1+ state, the mixed symmetry 2+ state, the second 2+ state of S-34 and so on are reported. (K.I.)