Empirical and Semi-Empirical Parameterization of Radiative Neutron Capture Cross Sections for Thirteen Actinides Across Three Energy Regimes

We present a systematic, experiment-only parameterization of the radiative neutron capture cross section σn, γ(E) for thirteen actinides of importance to reactor physics, fuel-cycle modeling and transmutation (232Th, 233U, 235U, 238U, 237Np, 239Pu, 240Pu, 241Pu, 242Pu, 241Am, 243Am, 244Cm and 246Cm). A total of 90,299 EXFOR points were reduced to a per-isotope tabular form and analyzed in three regimes whose boundaries follow standard nuclear-data conventions: thermal (E < 0.5 eV), resonance (split into RRR, 0.5 eV–1 keV and URR, 1–100 keV) and fast (0.1–1.0 MeV). In every regime, an empirical and a semi-empirical description are fitted to the same data under a common point-uncertainty model; the effect of dataset-wide normalization offsets is assessed separately by refits with per-dataset log-normalization parameters. Models are compared by reduced χ2, AIC/BIC and—in the URR—by dataset-level hold-out validation, and every derived quantity carries both a delta-method uncertainty and a dataset-level resampling 95% interval. In the thermal region the bound-level-plus-first-resonance form recovers first-resonance energies for 239Pu, 241Pu, 237Np, 241Am and 243Am to more than 3% from cross-section data alone; in the URR the Porter–Thomas-corrected statistical model is preferred on AIC for 7 of 12 nuclides, with fission competition included for the four fissile targets, but on dataset-level hold-out for only 3 of 5; and in the fast region the closed-form black-nucleus statistical model used here fails for 232Th, 238U and 237Np, whereas a default TALYS calculation reproduces the energy dependence for 232Th and 238U after a single normalization, attributing the failure to the approximations of the closed-form model rather than to statistical-model theory. Dataset-level resampling intervals are up to eighty times wider than delta-method uncertainties, demonstrating that inter-experiment discrepancy—not counting statistics—dominates the uncertainty of the pooled actinide capture record.