Charge-exchange excitations of nuclei

The modern microscopic approaches used to describe the properties of nuclear charge-exchange excitations in the low-energy part of the spectrum, including the region of giant resonances, are reviewed. The results of calculations based on the theory of finite Fermi systems with exact allowance for the single-particle continuum are compared in detail with experimental data with the aim of extracting information about the effective nucleon--nucleon interaction and the local quasiparticle charge e/sub q/[sigmatau] with respect to the spin--isospin field. The part played by this charge in quenching the strength of spin-flip transitions is discussed. Strength functions characterizing the distribution of the strengths of transitions of different multipolarities over the excitation spectrum are given for a number of nuclei