Pygmy dipole response of proton rich argon beyond the random phase approximation

C. Barbieri, E. Caurier, K. Langanke, G. Martínez-Pinedo

Published 2007-12-19Version 1

The occurrence of a pygmy dipole resonance in proton rich Ar-32 and Ar-34 is studied using the unitary correlator operator method interaction Vucom, based on Argonne V18. Predictions from the random phase approximation (RPA) and the shell model in a no-core basis are compared. It is found that the inclusion of configuration mixing up to two-particle--two-holes broadens the pygmy strength slightly and reduces sensibly its strength, as compared to the RPA predictions. For Ar-32 a clear peak associated with a pygmy resonance is found. For Ar-34, the pygmy states are obtained close to the giant dipole resonance and mix with it.