Helium Content of Beryllium

Abstract

THE abnormally high helium content of several Palæozoic beryls discovered by Strutt¹ has recently been verified by Paneth and Guenther.² Atkinson and Houttermans have discussed³ the proton bombardment in the interior of the stars and the possible formation of Be⁸ which being probably unstable would yield two helium nuclei, and Lord Rayleigh⁴ suggests that the high helium content of beryls might conceivably be due to Be⁸ which has existed in geological times even if not known to exist at present. This implies, however, that Be⁸ existed at least in Palæozoic times, a relatively very late period since the star state and proton bombardment. The recent experiments of Cockcroft and Walton⁵ would indicate that Be⁸ can have only a very short life period. A possible source of excess helium might be found, however, in the following proposed mechanism: Be⁹ + α-particle = 3 He nuclei + neutron, and treating this in a similar manner to Chadwick's treatment,⁶ the maximum energy of the emission of the neutron is about 5.2 × 10⁶electron volts as compared to 5.7 × 10⁶ found in Chadwick's experiments and a maximum energy of about 8 × 10⁶ electron volts given by the equation assuming C¹² is the end product. If both mechanisms are possible we might then expect two groups of neutrons of different maximum energies. In the Palæozoic beryl, about 300 × 10⁶ years old, radium was detected but no thorium. The α-particle of greatest kinetic energy is therefore from Ra C' which would give a maximum energy to the neutron of about 7.7 × 10⁶ volts or about 10.5 × 10⁶ if C¹² is the end product.