Letter of Intent to the ISOLDE and Neutron Time-of-Flight Committee Study of the Pygmy Dipole Resonance using an Active Target May 31

In this letter of intent we propose to study the low-lying electric dipole strength in nuclei with neutron excess. The origin of this strength has been recently investigated in several theoretical and experimental works. Its presence can be explained with the existence of a collective excited state called pygmy dipole resonance. The study of this strength can be experimentally performed using hadronic or electromagnetic probes. Our proposal is to study the isoscalar electric dipole strength in long-lived nuclei using (α,α′) inelastic scattering reaction in inverse kinematics. For the experiment the use of an Active Target as SpecMAT is fundamental. The proposed physics case may open the way for new experiments in the near future, when radioactive ion beams with N/Z 1 will be available.