It is shown that a resonance of suitable position and width in the $J=1\mathrm{}$, $I=1\mathrm{}$ state of the pion-pion system can bring the dispersion-theoretic calculation of the isotopic-vector part of the nucleon electromagnetic structure into agreement with experiment. The calculation of the isotopic-vector part of the nucleon form factors involves in first approximation the pion form factor and the matrix element for the production by two pions of a nucleon-antinucleon pair. For the pion form factor we used a semiphenomenological solution based on the work of Chew and Mandelstam and involving two parameters related to the position and width of the resonance. For the $\pi +\pi \to N+\overline{N}$ amplitude we used the results of the preceding paper.

• Received 9 October 1959

DOI:https://doi.org/10.1103/PhysRev.117.1609