Disintegration of Beryllium by Electrons

The beryllium nucleus has been disintegrated by fast electrons whose energies exceeded the photoelectric threshold. The source of the electrons was a 1.8-Mv Van de Graaff generator. As was predicted by Guth, neutrons were produced, and the radioactivity which these neutrons induced in silver was used as a measure of the rate of disintegration. The possibility that the observed disintegration was not due to the direct action of the electrons, but resulted from stray x-rays, or x-rays produced in the beryllium by the electrons was eliminated. The yield curve for disintegration by electrons was obtained, and fixed the threshold for this process at 1.63±{}0.05 Mev. At 1.73 Mev the cross section was found to be 10^-31 cm², in good agreement with theory.The yield curve for photodisintegration by continuous x-radiation was also obtained, and the threshold was found to be identical with that for disintegration by electrons.