Spin Excitation of Nuclei by Pions

The energy dependences of the spin-dependent and spin-independent free πN interaction are examined using updated πN phase shifts over a wide range of energies. PWIA and DWIA calculations for the purely spin-dependent transition to the 9/2+ state in 13C (9.5 MeV) are used to determine the modifications of this energy dependence by the π-nuclear distortions. It is concluded that the nature of the πN interaction in nuclei should be studied at energies where the absorption is smaller than at the (3,3) resonance. Calculations are also presented for cross sections and asymmetries of elastic scattering of pions from polarized 3He at incident energies T π between 100 and 500 MeV.