Heavy ion excitation of giant resonances

The Coulomb interaction between heavy ions is very well known, in contrast to the strong nuclear interaction. This fact has been used for a long time to study aspects of nuclear structure using sub-barrier bombarding energies, where the nuclear interaction plays a minor role. However, at such low energies the electromagnetic interaction does not carry virtual photons with high frequencies to access the excitation of giant resonances with appreciable cross sections. This can be achieved by increasing the bombarding energy. At intermediate energies (∼ 100 MeV/nucleon) measurements of the inelastic angular distribution (1--6 degree) are possible, while at relativistic energies (> 1 GeV/nucleon) only the measurement of total cross sections is accessible. Here they will discuss the most relevant problems in the description of the reaction mechanisms of heavy ion excitation of giant resonances, namely, the competition between Coulomb and nuclear excitation and the effects of relativity. Relativity brings new features to the scattering process, like the enhancement of the magnitude of the Coulomb excitation cross sections to several barns at very high energies. Heavy ions are also especially suited for Coulomb excitation since the cross sections depend on the square of the charge of the ions