Abstract
The differential cross sections, asymmetry ratios and recoil-nucleon polarizations of pion photoproduction on protons and neutrons below 500 MeV have been studied. It is shown that the dispersion theory of Berends, Donnachie and Weaver is unfavorable because of their inadequate treatments of the P11 (1470) and D13 (1518) resonances. The phenomenological analysis shows that the effect of the Roper P11 (1470) resonance is negligible and the isovector amplitude is dominant in the multipole amplitudes leading to the final D13 state. The experimental data are also favorably explained by the crude dispersion-theoretical model of Schmidt et al.
