Some possibilities are explored for the theoretical explanation of the angular distribution of $D+D$ reaction products. The variation with energy is ascribed entirely to differences in the centrifugal barriers encountered by the bombarding particles responsible for the isotropic and non-isotropic components. The detailed data on the proton distributions at low energies appear to be explained in terms of an asymmetric part produced by $P$-waves superposed on isotropic emissions caused by $S$-waves. However, ordinary extrapolation of this to higher energies gives much less symmetric distributions than experimentally found at such energies for the emission of neutrons. If the experiments are correct as interpreted, then they appear to show that spin-orbit coupling plays a large part in the reactions. In that case, an isotropic component produced by incoming $P$-waves grows in importance with energy and accounts for the increasingly parallel growth of the isotropic and asymmetric emissions.

• Received 12 January 1948

DOI:https://doi.org/10.1103/PhysRev.73.822