Quantum mechanical description of excitation energy distribution of the reaction residue in nucleon-induced inclusive one-nucleon knockout reactions

Abstract

Understanding of inclusive one-nucleon knockout reactions for long-lived fission fragments (LLFPs) is crucial for nuclear transmutation studies. However, the particle and heavy ion transport code system (PHITS) severely overshoots the inclusive one-nucleon knockout cross sections sigma_-1N. Therefore development of a reaction model for describing the inclusive one-nucleon knockout processes is necessary. A key is specification of the position and the momentum of a nucleon inside a nucleus to be struck by the incident nucleon. In this paper the semiclassical distorted wave model incorporating the Wigner transform of the one-body nuclear density matrix is applied to the calculation of excitation energy distributions of reaction residues. Decay of a residue is described by introducing a threshold parameter for the minimum excitation energy of it. With reasonable values of the parameter, the measured sigma_-1N for several LLFPs are reproduced by the proposed reaction model. The incident energy dependence of sigma_-1N is found to be governed by that of the nucleon-nucleon cross sections at energies higher than about 75 MeV. At low energies, the nuclear absorption and the Coulomb penetrability also become important. The energy dependence of neutron-induced sigma_-1N is predicted and found to be quite different from that of proton induced one. The proposed reaction model is shown to be promising in discussing the energy dependence of nucleon-induced inclusive one-nucleon knockout processes. The energy dependence of the measured sigma_-1p for 107Pd above 100 MeV is, however, not explained by the present calculation.