Collective spin-isospin excitations in nuclei

Charge exchange reactions at intermediate energies are used to study the spin-isospin response of nuclei. A microscopic analysis of complete forward angle (p,n)-spectra is presented for the reactions 208Pb(p,n) and 90Zr(p,n) at E=200 MeV. It is shown that the spectra can be nearly quantitatively understood in terms of microscopic nuclear structure and reaction models. An analysis of the 90Zr(3He,t)-spectra at E=600 MeV gives first evidence for the existence of an isovector spin-flip monopole state at Ex=30 MeV in 90Zr. The strong excitation of this monopole strength in the (3He,t)-reaction is a result of the surface character of the (3He,t)-reaction. (author). 24 refs., 4 figs