The Giant Dipole Resonance in Ar-Isotopes in the Relativistic RPA

Abstract

The isovector giant dipole resonance in Ar-isotopes is studied in the framework of the relativistic random phase approximation starting from effective Lagrangians originally proposed for describing nuclear ground states. The calculations are done with the parameter set TM1 which satisfactorily describes the ground states of stable and unstable nuclei up to the drip lines. It is found that the isovector dipole strength in nuclei near drip lines is split into two components: one peaks at the normal giant dipole energy, the other is located at low energy. The lower dipole state is due to the weakly bound neutron (or proton) excitation, which may cause large cross-sections in collisions with heavy nuclei by Coulomb excitation.