Competing particle–hole excitations in ³⁰Na: Constraining state-of-the-art effective interactions

The odd–odd nucleus ³⁰Na is studied via a one-proton, one-proton–one-neutron and one-neutron removal reaction using an intermediate-energy ³¹Mg, ³²Mg and ³¹Na radioactive ion beam, respectively. Combining high-resolution γ-ray spectroscopy with the selectivity of the three reaction mechanisms, we are able to distinguish multiple particle–hole configurations. Negative-parity states in ³⁰Na are observed for the first time, providing an important measure of the excitation of the 1p1h/3p3h configuration and hence the sd–pf shell gap. The extracted band structures and level energies serve as invaluable input for the theoretical refinement of the effective interactions used in this region