Yield curves have been obtained for eight of the more important reactions of ${\mathrm{Li}}^6$ and ${\mathrm{Li}}^7$ produced by proton and deuteron bombardment in the energy range from 200 to 1000 kev. Each curve was obtained with an accuracy of about five percent, and a set of intercomparisons served to determine the relative yields between the different reactions within 20 percent. A special set of observations on a single reaction then gave the absolute yield for all the reactions within a factor of about three. An investigation was made of the reactions involved in the formation and decay of ${\mathrm{Li}}^8$, the mass of which was found to be 8.02499±0.00020. The range-distribution of the delayed alpha-particles from ${\mathrm{Li}}^8$ was measured and the interpretation of this distribution is discussed. Observations on the reaction ${\mathrm{Li}}^6+n\to {\mathrm{He}}^4+{\mathrm{H}}^3$ gave a value of 4.97 Mev for the reaction energy as compared to a value of 4.56 Mev derived from the masses involved. No evidence could be obtained for the production of ${\mathrm{Li}}^8$ by the process ${\mathrm{Li}}^7+n\to {\mathrm{Li}}^8$. Measurements of the energies of the neutrons produced by deuteron bombardment of ${\mathrm{Li}}^6$ indicated that ${\mathrm{Be}}^7$ is formed by the reaction ${\mathrm{Li}}^6+{\mathrm{D}}^2\to {\mathrm{Be}}^7+n$. Further experiments showed that ${\mathrm{Be}}^7$ is radioactive and is converted to ${\mathrm{Li}}^7$ by $K$-electron capture. It was found that this process is followed by gamma-ray emission in roughly ten percent of the transitions.

• Received 13 September 1938

DOI:https://doi.org/10.1103/PhysRev.54.657