Free Antineutrino Absorption Cross Section. II. Expected Cross Section from Measurements of Fission Fragment Electron Spectrum

A measurement of the electron spectrum from the thermal neutron fission of ${\mathrm{U}}^{235}$ is described. From this spectrum the antineutrino spectrum is calculated, and on the basis of the two-component theory of the antineutrino a predicted average cross section for the absorption of antineutrinos by protons is (6.1±1)×${10}^{-43\mathrm{}}$ ${\mathrm{cm}}^2$/fission. This agrees with the measured cross section of (6.7±1.5)×${10}^{-43\mathrm{}}$ ${\mathrm{cm}}^2$/fission. The four-component theory of the antineutrino would have predicted (3.05±0.5)×${10}^{-43\mathrm{}}$ ${\mathrm{cm}}^2$/fission.