NEUTRON DEFORMATION PARAMETER FROM COMPARATIVE-STUDY OF PI+ AND PI- INELASTIC-SCATTERING

Differential cross sections for the excitation of the 2+ state in O18 by 230-MeV pions are found to be about 70% larger for - than for +. Since the -nucleon interaction at this energy is dominated by the (3,3) resonance, it is concluded that the results imply that Rn1.3Rp, or alternatively, that (R)n (valence neutrons) 3(R)c(core), where is the deformation parameter and R the equilibrium radius of the deformed potential. We believe that these results constitute the first example of measurement of the neutron deformation parameter. © 1978 The American Physical Society.