Gamma-ray emission from multistep compound reactions

Abstract

The multistep compound formalism of Feshbach, Kerman, and Koonin has been extended to include y-ray emission. By allowing the first few simple preequilibrium bound states to decay via electromagnetic transitions rather than particle emission, the large number of high-energy y rays observed in the experimental data can be understood. It is assumed that single-particle and -hole transitions lead to the emission of y rays, and radial matrix elements for such transitions are estimated by exploiting the inverse process, photoabsorption.Reactions of 14-MeV neutrons with ' Co, 'Nb, and "'Ta are analyzed and it is found that between 20% and 50% of cross sections for high-energy y-ray emission can be accounted for by the multistep compound mechanism. 421652

Cluster-Îş competition in the Iwamoto-Harada-Bisplinghoff model

“…In some future, however, experimental data may become measurable at energies above [15][16] MeV (the present experiments of the Oslo group usually end at about 7-8 MeV due to very low cross sections). Then the pre-equilibrium contribution to the γ emission prior to α's has not only to be taken into account, but it plays the essential role.…”

“…Significant improvement was the incorporation of spin into the formalism of the pre-equilibrium exciton model [14,15], which enabled also pre-equilibrium calculations leading to discrete states. However, we shall restrict our present calculations to the spin-independent description only.…”

Radiative nucleon capture - a dual approach

“…The study of excitation functions extended the applicability of the model to energies from few MeV to about 30 MeV. Significant improvement was achieved by the incorporation of spin into the formalism of the pre-equilibrium exciton model [8,9], which enabled also pre-equilibrium calculations leading to discrete states and the comparison to the direct-semi-direct model calculations.…”

Hard gamma emission close to the GDR energy region

“…The study of excitation functions of both neutron-and proton-induced reactions [8,9,10,11] extended the applicability of the model to energies starting from few MeV to about 30 MeV. Significant improvement was the incorporation of spin into the formalism of the pre-equilibrium exciton model [12,13], which enabled also pre-equilibrium calculations leading to discrete states [14] and the comparison to the direct-semi-direct model calculations [3].…”