Excitation of Low Lying Dipole States (Pygmy) via Nuclear Field in Exotic Nuclei

We review recent work done in the study of the excitation of low lying dipole states, known also as Pygmy resonance, via nuclear potential. The use of isoscalar probe is enabled by the strong mixing of isoscalar and isovector components which is a distinctive property of these states. The calculation of the excitation cross section is performed within a semiclassical model where microscopic (Random Phase Approximation (RPA)) transition densities as well as form factors are used. The use of proper microscopic form factor is demanded if one does not want to jeopardize the agreement between the theory and experiment.