New approach to analyzing and evaluating cross sections for partial photoneutron reactions

Abstract

The presence of substantial systematic discrepancies between the results of different experiments devoted to determining cross sections for partial photoneutron reactions—first of all, (γ, n), (γ, 2n), and (γ, 3n) reactions—is a strong motivation for studying the reliability and authenticity of these data and for developing methods for taking into account and removing the discrepancies in question. In order to solve the first problem, we introduce objective absolute criteria involving transitional photoneutron-multiplicity functions F ₁, F ₂, F ₃, …; by definition, their values cannot exceed 1.0, 0.5, 0.33, …, respectively. With the aim of solving the second problem, we propose a new experimental-theoretical approach. In this approach, reaction cross sections are evaluated by simultaneously employing experimental data on the cross section for the total photoneutron yield, σ ^expt(γ, xn) = σ ^expt(γ, n) + 2σ ^expt(γ, 2n) + 3σ ^expt(γ, 3n) + …, which are free from drawbacks plaguing experimental methods for sorting neutrons in multiplicity, and the results obtained by calculating the functions F ¹_theor , F ²_theor , F ³_theor , … on the basis of the modern model of photonuclear reactions. The reliability and authenticity of data on the cross sections for (γ, n), (γ, 2n), and (γ, 3n) partial reactions—σ ^eval(γ, in) = F ^theor _i σ ^expt(γ, xn)—were evaluated for the ⁹⁰Zr, ¹¹⁵In, ^{112,114,116,117,118,119,120,122,124}Sn, ¹⁵⁹Tb, and ¹⁹⁷Au nuclei.