Absolute cross sections for (γ,n) transitions in lead, bismuth, and terbium

Absolute cross sections of (γ,n) transitions in lead, bismuth, and terbium were measured using thermal neutron capture photons, and a high resolution neutron spectrometer. The measured (γ,n) cross sections were compared with predictions of the Direct-Semi-Direct (DSD) and the compound nucleus (CN) models, and were found to be generally underestimated by the DSD calculations and closer to the predictions of the CN models. Some of the (γ,n) cross sections in lead and bismuth were found to be comparable in magnitude to the extrapolation from the tail of the giant dipole resonance.