Excited States of the Nucleon

Abstract

The quantum numbers of the higher resonances in pion-nucleon scattering belonging to the nucleon and 3-3 isobar trajectories are shown to arise from the exchange of the nucleon and pion-nucleon resonances themselves. In particular the members of the nucleon trajectory are created principally by forces due to the exchange of members of the 3-3 isobar trajectory and vice versa. The quantum numbers obtained from dynamical considerations agree completely with those conjectured on the basis of Regge pole considerations. The dynamical scheme is approximately symmetrical under interchange of the two trajectories.