The Beta-Ray Spectra ofLi8andB12

Cloud chamber measurements have been made on the beta-ray spectra of ${\mathrm{Li}}^8$ and ${\mathrm{B}}^{12}$. The use of strict criteria in the selection of tracks for measurement is thought to have reduced preference for tracks at one or the other end of the spectrum. Separate measurements near the upper limits give for both spectra upper limits by inspection of 12.0±0.6 Mev. Evidence is presented that the protons emitted during the formation of ${\mathrm{Li}}^8$ have nearly zero energy. It is thus possible to determine the energy available in the radioactive disintegration of ${\mathrm{Li}}^8$ into an electron, neutrino and two alpha-particles. Comparisons are made between the experimental ${\mathrm{Li}}^8$ spectrum and those predicted by using the K-U and Fermi theories in conjunction with the recently measured alpha-particle distributions. It is shown that the K-U theory demands a reaction energy 5 Mev greater than that which is available. An indication is given that the protons emitted during the formation of ${\mathrm{B}}^{12}$ have an energy of at least 1 Mev, while a proton energy of nearly zero is required if the K-U upper limit, 14.5 Mev, is correct.