Negative parity levels of 16O from three-body forces

We have performed Tamm–Dankoff and RPA calculations of the odd excited states of 16 O on the Hartree–Fock basis, using various effective interactions in which a Skyrme-type three-body term simulates the density dependence. We show that although these forces lead to good results for the HF ground state they are not appropriate for odd parity excited states. In particular if the strength of the three-body term is too great, the 2 − level becomes imaginary. This in fact occurs for the interaction Vautherin–Brink I, which shows that the spherical HF solution with this force is unstable.