On the Neutron-Proton Scattering Cross Section

The sensitivity of the theoretical neutron-proton scattering cross section to possible variations in the quantities defining the potential has been investigated in the energy range from 0 to 6 Mev. It is found that in this energy range the variations in exchange or tensor character and range of the potential which are consistent with what is known about the interaction do not result in so large a modification of the predicted cross section as do variations in shape.

A well resembling a Yukawa potential ($A \exp \frac{(-\alpha r)}{r}$) is found to yield a cross section at 6 Mev which is 10 percent lower than that given by a square well fitted to the epithermal neutron cross section and the binding energy of the deuteron. The Yukawa well is in better agreement with experiment than is the square well. One of the constants entering into the determination of the potential is the epithermal neutron scattering cross section in hydrogen. We have determined this by extrapolating the data of Frisch with the aid of the theory, and obtained a value of 20.8×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$.