GAMMA–ALPHA REACTIONS IN THE LIGHT NUCLEI OF NUCLEAR EMULSIONS

Abstract

Ilford E.1 nuclear emulsions were loaded with various amounts of glycerine to vary the content of carbon and of oxygen, and were then irradiated in the beam of the University of Saskatchewan betatron. The numbers of single alpha-particle tracks and of four-pronged alpha-particle stars were correlated to the oxygen content of the plates and the number of three-pronged stars to the carbon content. The yields for the reactions O16(γ, α)C12, O16(γ, 4α), and C12(γ, 3α) for bremsstrahlung of 24-Mev maximum energy were found without confusion with reactions in other nuclides of the emulsion and without having to rely on momentum balances for identification of the events. It was shown that the method of identification of 016(γ, α)C12 events by the measurement of the track of the C12 was not reliable. The large number of alpha tracks in the energy range 4 to 5 Mev, few of which showed a C12 track, was shown to be due largely to reactions in O16. It was also possible, by irradiating emulsions at 17- and at 24-Mev maximum bremsstrahlung energy, to find the energy levels in O16 and in C12 through which the reactions passed.