Giant resonances in single and double charge exchange

A long-standing issue in nuclear physics is whether or not multiple excitations of the giant-dipole resonance do exist. Recent studies at LAMPF using pion-induced double-charge exchange reactions show the existence of previously unobserved giant resonances in the continuum at high-excitation energies. Based on their energies, characteristic angular distributions, and the cross sections at which the resonances are observed, they have been identified as two different types of double-collective-excitation modes of the nucleus: (1) The isovector giant-dipole resonance built on the isobaric analog state and (2) the isovector giant-dipole resonance built on the giant dipole. In this report we will discuss the general features of the new resonances as they have emerged from DCX experiments performed recently at LAMPF. 12 refs., 7 figs