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

The odd–odd nucleus 30 Na is studied via a one-proton, one-proton–one-neutron and one-neutron removal reaction using an intermediate-energy 31 Mg, 32 Mg and 31 Na 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 30 Na 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. [ABSTRACT FROM AUTHOR]