First observation of an excited state in the neutron-rich nucleus Na-31

The first excited state in the neutron-rich N=20 isotope Na-31 was observed at 350(20) keV via intermediate energy heavy-ion scattering, which is dominated by the Coulomb excitation mechanism. This state appears to be a rotational excitation built on a strongly deformed ground state. The yield of the gamma ray deexciting this state can be reproduced by a shell model calculation which takes nu (f(7/2), p(3/2)) intruder configurations into account.