(α, n) reactions in cascade γ-transitions

Abstract

The ratios of the cross sections for the formation of the ground and isomeric states in reactions on¹⁰⁷Ag,¹⁰⁹Ag, and¹¹³In are calculated based on the assumption that at low energies the (α, n) reaction proceeds via a) formation of the compound nucleus, b) evaporation of a neutron, and c) cascade γ-transitions. The number of cascade γ-quanta and the distribution of the excitation energy between the γ-quanta and the neutron is not postulated beforehand (as is usually done), but is calculated based on the statistical theory. By comparing with experiment, the parameter of the spin-dependence of the density of nuclear states is found. It is shown that the average number of γ-quanta in the cascade increases approximately linearly with the energy of the α particles. The energy spectrum of the γ-quanta in the (α, n) reaction is calculated. The distribution of γ-quanta has a maximum at low energies (1 MeV), which, as the energy of the primary particles is increased, moves slowly into the higher energy range while broadening at the same time.