The collisions of neutrons with nitrogen nuclei

Abstract

Elsewhere in these ‘Proceedings’ experiments are described in which the radiations excited in certain light elements under α-particle bombardment are examined in great detail by means of the valve counter. On the basis of such experiments in the case of beryllium Chadwick was first led to suggest that the radiation, previously believed to be of the γ-ray type, in fact consisted of particles of zero resultant charge and unit mass. In the present paper a study of this radiation is described, in which the expansion chamber is employed. Initially visual observations were made with a Shimizu chamber and the production in air of recoil atoms demonstrated. A more detailed investigation has now been completed in which the usual photographic methods have been employed. Curie and Joliot likewise used an expansion chamber in preliminary experiments to establish the ejection of protons from paraffin under the influence of the radiation from beryllium, and later published photographs of recoil tracks both of protons and helium nuclei. Similar photographs were published by Rasetti, whilst Auger has also given examples of the tracks of protons produced in this way. Kirsch and Rieder have made more extensive experiments, using visual methods throughout. In certain cases electron tracks also were reported. This aspect of the problem is dealt with by Dee in the paper next after this.