Collision Cross Sections of Carbon and Hydrogen for Fast Neutrons

Experiments are described by means of which the collision cross sections of carbon and hydrogen were determined for neutrons of nine different energies between 6 Mev and 22 Mev. The experimental method was such that data could be taken on groups of neutrons having energies within an interval small compared to the neutron energy, and at any energy produced by an energy heterogeneous source. The results are consistent with those of other observers at the four neutron energies in this range which have been previously investigated. A comparison with various theories shows that at high energies the observed hydrogen cross sections are about 10 percent larger than pure $S$-wave cross sections computed on the basis of a square well interaction between neutron and proton, and that they agree very well with the "symmetrical" theory of Rarita and Schwinger.