Symmetry energy from the nuclear collective motion: constraints from dipole, quadrupole, monopole and spin-dipole resonances

摘要

The experimental and theoretical studies of Giant Resonances, or moregenerally of the nuclear collective vibrations, are a well established domainin which sophisticated techniques have been introduced and firm conclusionsreached after an effort of several decades. From it, information on the nuclearequation of state can be extracted, albeit not far from usual nucleardensities. In this contribution, which complements other contributionsappearing in the current volume, we survey some of the constraints that havebeen extracted recently concerning the parameters of the nuclear symmetryenergy. Isovector modes, in which neutrons and protons are in opposite phase,are a natural source of information and we illustrate the values of symmetryenergy around saturation deduced from isovector dipole and isovector quadrupolestates. The isotopic dependence of the isoscalar monopole energy has also beensuggested to provide a connection to the symmetry energy: relevant theoreticalarguments and experimental results are thoroughly discussed. Finally, weconsider the case of the charge-exchange spin-dipole excitations in which thesum rule associated with the total strength gives in principle access to theneutron skin and thus, indirectly, to the symmetry energy.