Neutron capture studies of ²⁰⁶Pb at a cold neutron beam

Gamma-ray transitions following neutron capture in ²⁰⁶Pb have been studied at the cold neutron beam facility of the Budapest Neutron Centre using a metallic sample enriched in ²⁰⁶Pb and a natural lead nitrate powder pellet. The measurements were performed using a coaxial HPGe detector with Compton suppression. The observed γ-rays have been incorporated into a decay scheme for neutron capture in ²⁰⁶Pb. Partial capture cross sections for ²⁰⁶Pb(n, γ) at thermal energy have been derived relative to the cross section for the 1884 keV transition after neutron capture in ¹⁴N. From the average crossing sum a total thermal neutron capture cross section of 29_-1⁺² mb was derived for the ²⁰⁶Pb(n, γ) reaction. The thermal neutron capture cross section for ²⁰⁶Pb has been compared with contributions due to both direct capture and distant unbound s-wave resonances. From the same measurements a thermal neutron-induced capture cross section of (649 ± 14) mb was determined for the ²⁰⁷Pb(n, γ) reaction.