Evaluated Cross Sections for Neutron Scattering from Natural Carbon Below 2 MeV Including R Matrix Fits to ¹³C Resonances

The ENDF/B-V differential cross sections for neutron scattering from natural carbon below 2 MeV, recommended as standards for measurements and based on an R matrix analysis for ¹²C using natural carbon data, are revised to include ¹³C resonances for high-resolution applications. The recommended ¹³C cross sections are also based on an R matrix analysis of the available data. The 0.1529- and 1.736-MeV resonances rise above the natural carbon background by 7 and 1%, respectively. The angular distributions of the elastically scattered neutrons from ¹³C are generated by the R matrix theory. The final recommended cross sections and Legendre coefficients of angular distributions for natural carbon, adopted for ENDF/B-VI, are tabulated.