Speaker
Description
This work presents evidence for statistically significant oscillations in neutron-capture cross sections within the resolved-resonance region, challenging the conventional assumption that fluctuations are entirely random as predicted by random matrix theory (RMT). Using autocorrelation and cosine-fitting techniques, neutron-capture data for 21 nuclides were analyzed over a broad range of resonance energies. Highly significant oscillatory behavior was observed in 13 of the 21 cases studied, with nine exhibiting significance levels greater than 5σ. The oscillations account for an average of 10.9% of the reduced neutron-capture cross section and display periods ranging from approximately 68 to 2380 eV. These results suggest that deviations from RMT are not isolated anomalies, but instead reflect a widespread physical mechanism absent from current descriptions of neutron-induced reactions. The study was motivated in part by observations from previous DICER (Device for Indirect Capture Experiments on Radionuclides) measurements at the Los Alamos Neutron Science Center, where unexpected resonance structures and correlations in neutron transmission data hinted at nonrandom behavior in neutron-capture processes. DICER’s unique capability to perform high-resolution neutron transmission measurements on small and radioactive samples provided critical insight into resonance phenomena that inspired the present investigation. By extending these observations to a large body of neutron-capture data, the present work demonstrates that oscillatory structure appears across a wide mass range and in both capture and fission reactions. The existence of these oscillations has important implications for nuclear statistical models, evaluated nuclear data libraries, and applications in nuclear astrophysics, reactor physics, and national security. Overall, the results indicate that neutron-induced reaction cross sections contain previously unrecognized systematic structure that warrants both theoretical explanation and further experimental investigation.