On the Comparison of Proton-Proton and Proton-Neutron Interactions

Based on the data of Tuve, Heydenburg and Hafstad for the scattering of protons by protons and that of Amaldi and Fermi for the scattering of neutrons by protons a comparison of the two interactions is made. The present comparison is made more accurately than previously and allows for the uncertainty in the chemical factor $C$ which is used in the interpretation of the neutron-proton experiments. The results are substantially in agreement with those of Breit, Condon and Present, the two interactions being very nearly equal. A slight excess of neutron-proton attraction over that between protons is indicated by the present calculation. Fermi's conclusion that the singlet $S$ level of deuterium is virtual is reexamined by taking into account the effect of the range of force and of the chemical factor on the mean life of neutrons in an atmosphere of protons. Experiment agrees better with a virtual than with a real level. Nevertheless the evidence for its virtual character is not so good as to exclude completely the possibility that it is real. Tests by means of which a real level could be found if present are discussed.