Application of relativistic continuum random phase approximation to giant dipole resonance of ^208 Pb and ^132 Sn

The relativistic continuum random phase approximation (RCRPA) is applied to describe the properties of isovector giant dipole resonances (IVGDR) in ^208 Pb and ^132 Sn with NL3 effective interaction. We analyze the strength distribution, various sum rules, centroid energies and the integral photoabsorption cross sections of the pygmy dipole resonance (PDR) and giant dipole resonance (GDR), the results are compared to the values obtained by discretized RRPA and available experimental data. Difference between the results obtained by RRPA and RCRPA is found, which may due to the different ways in treating the contribution of continuum. The calculated centroid energies of GDR can reproduce the experimental data well for ^208 Pb and ^132 Sn. A better agreement with photoabsorption cross section data is obtained for ^132 Sn in the RCRPA calculation. By correlating the excitation energy (the electric dipole polarizability) of GDR to the nuclear matter properties, we could constrain the density dependence of symmetry energy. The deduced nuclear symmetry energy is located in the range 30.3–36.5 MeV (30.8–32.8 MeV), and the slope parameter L essentially covers the range of 40.1–106.1 MeV (40.0–63.0 MeV) at the saturation density.