Cross sections of the photoneutron reaction for 141Pr and 186W nuclei, estimated from physical criteria of data reliability

Abstract

Using objective physical criteria for data reliability, cross sections of partial photoneutron reactions (γ, 1n), (γ, 2n) and (γ, 3n) that are free of the shortcomings of neutron multiplicity sorting methods used on beams of quasimonoenergetic annihilation photons are obtained for 141Pr and 186W nuclei. Evaluation is performed using the experimental–theoretical method (ETM), based on the experimental cross section of neutron yield reaction σexp(γ, xn) = σexp(γ, 1n) + 2 σexp(γ, 2n) + 3 σexp(γ, 3n) + … and ratios F i theor= σtheor(γ, in)/σtheor(γ, xn) calculated within the combined model (CM) of photonuclear reactions, which stipulates that σeval(γ, in) = F i theor σexp(γ, xn). It is found that for 141Pr and 186W, ratios F exp i do not contradict the data reliability criteria only at energies up to ~21 and ~22 MeV, respectively. At the same time, there are notable discrepancies between F i theor and F exp i, and thus between the evaluated and experimental cross sections of reactions. It is shown that the discrepancies between the evaluated and experimental cross sections are due to the assumed unreliable experimental distribution of neutrons in the channels with multiplicities 1, 2, and 3.