Thermal neutron capture γ-ray spectrum of lanthanum

Abstract

The thermal neutron capture gamma rays from the reaction 139La(n, γ)140La were investigated using a pair spectrometer and the tangential facility at the McMaster University Nuclear Reactor. A large number of previously unreported transitions have been observed from which details of the 140La structure are inferred. The level density is found to be consistent with a statistical model encompassing nuclear temperature. The reduced E1 strength function of 140La was found to be (1.4 ± 0.4) × 10−9 MeV−3. The giant dipole resonance model seems to overestimate the E1 strength in this nucleus. The separation energy of 140La is found to be 5161.00 ± 0.05 keV.