The disintegration of boron by slow neutrons

Abstract

Photometrical measurements of the photographic images of cloud tracks of the disintegration of boron by slow neutrons, have enabled the ranges of both the He and the Li particle to be determined. We find that the He particle has a range of 7·0 ± 0·3 mm. and the Li particle a range of 4·3 ± 0·2 mm. in standard air. We deduce that the 7 Li nucleus is usually formed in an excited state, with energy of excitation of either 0·5 or 0·8 M.e.V. The wide latitude in excitation energy is due to the uncertain state of our knowledge of the energy-range relation for α-particles.