Resonant Neutron Capture in 139La

Abstract

The neutron capture cross section of 139La has been measured with high energy resolution between 2· 5 and 90 ke V using the capture cross section facility at the 40 m station on the Oak Ridge Electron Linear Accelerator. Individual resonances were analysed to 15 keV and the average s- and p-wave radiative widths deduced were <Γ_γ>_s = 55±6meV and <Γ_γ>_p = 4O±7meV. The p-wave neutron strength function obtained was S1 = (0'30±0'1O)x 10-4 ? The s-wave resonances decay strongly to final f-wave states via a postulated doorway state mechanism. The transition strengths for these decays are not correlated with the neutron widths of the initial states.