The giant dipole resonance and the symmetry energies

We analyze, by means of semi-classical evaluations of RPA sum rules of the dipole strength, the role of the volume and surface symmetry energies epsilon sub(delta)sup(v) and epsilon sub(delta)sup(s) in the fragmentation of the calculated total photo cross-section. Comparison with experiment favors values in the range epsilon sub(delta)sup(v) = 35 to 37 MeV and epsilon sub(delta)sup(s) =-90 to -120 MeV, i.e. a ratio /epsilonsub(delta)sup(s)/epsilon sub(delta)sup(v)/ approximately 3