Excitation of γ-Rays by Neutrons. III.

Abstract

The emission of γ-rays from numerous substances traversed by fast neutrons (2 m.e v.) has been confirmed, and the relative cross sections of the effect have been determined for 32 elements and are tabulated in Table I. The absolute value of the cross sections could only be estimated very roughly and may probably be of the order of 5×l0^-25 cm² for Cu. For six elements, Sn, Cd, Zn, Cu, Ni, and Fe, which emit γ-rays most abundantly, the quantum energiens of the radiations have been determined by the absorption curve of secondary electrons using the usual method of coincidence of two counters. They are all of very similar character and though the energy of most of the secondary electrons lies under the kinetie energy of the primary neutrons there were some indications of the presence of harder components Absorption of secondary electrons due to γ-rays excited by slow neutrons were also obtained for the above six elements. In every ease, except Sn, the rays are distinctly harder in the case of slow neutrons