Photodisintegration of the alpha-particle and the inverse processes

The partial cross-sections for photodisintegration of the alpha-particle are calculated in the usual first-order perturbation theory approximation, utilizing the symmetry properties of the wave functions of the alpha-particle and of the various product nuclei. From these results the cross-sections for radiative capture of protons by $^{3}$H, neutrons by $^{3}$He, and deuterons by deuterons, can be deduced. It is found that (a) the yield of gamma-rays from the $^{3}$H(p$\gamma $) $^{4}$He reaction should increase with bombarding energy up to several MeV; (b) the radiative capture cross-section of $^{3}$He for thermal neutrons should be negligible; and (c) the radiative cross-section for the D + D reaction should be smaller than that for the T + P reaction at corresponding energies by a factor of about 10$^{-3}$. Conclusion (a) is discussed in the light of recent experiments at Los Alamos, which purport to establish the existence of an excited state of the alpha-particle.