ABSTRACT
A variety of resonant states, at energies larger than the nucleon separation energy have been observed throughout the mass table. They are known as giant resonances or giant vibrations, in keeping with the fact that they display large cross sections, close to the maximum allowed by sum rule arguments, implying that all nucleons participate in the vibration. Progress in the study of the giant dipole vibrations was made when monoen-ergetic photon beams became available. The type of quadrupole deformation displayed by the system can be deduced from the ratio of the areas subtended by the higher and lower components of the giant dipole resonance. The first giant resonance discovered in hadron scattering was the giant isoscalar quadrupole vibration. The excitation of the giant monopole and quadrupole resonances has been also studied in inelastic processes induced by heavy ions. The basic property of photon decay is its extreme sensitivity to the multipolarity of the giant resonance.
