Disintegration of Atomic Nuclei

Abstract

SINCE the discovery that high speed protons are emitted from the nuclei of a number of light elements by a close collision with an particle, it has been a matter of great interest to understand the mechanism of these collisions and particularly the fate of the bombarding particle. Dr. Chadwick and I have shown that the protons are emitted in all directions relative to the bombarding particles, but with greater velocity in the forward direction. This difference of velocity was ascribed to the effect of recoil of the nucleus, and assuming that the law of conservation of momentum, but not of energy, holds in such collisions, we were able to calculate from the experimental data the distribution of momentum between the particle, proton, and nucleus after the collision. These calculations showed that the velocity of the escaping particle was small for nitrogen, sodium, aluminium, and phosphorus, but considerable for boron and fluorine. Unfortunately, on account of the small number of particles, it is difficult to determine accurately the velocity of the proton in different directions, but, with accurate data, this method should prove useful in throwing light on the distribution of momentum amongst the particles concerned in the collision.