Radiative-capture cross sections for the La 139 ( n , γ ) reaction using thermal neutrons and structural properties of La 140

摘要: A set of prompt partial $\ensuremath{\gamma}$-ray production cross sections from thermal neutron capture were measured for the $^{139}\mathrm{La}(n,\ensuremath{\gamma})$ reaction using a guided beam subthermal (thermal and cold) neutrons incident on $^{\mathrm{nat}}\mathrm{La}_{2}{\mathrm{O}}_{3}$ target at Prompt Gamma Activation Analysis facility Budapest Research Reactor. Absolute $^{140}\mathrm{La}$ determined relative to well-known comparator $^{35}\mathrm{Cl}(n,\ensuremath{\gamma})$ irradiation stoichiometric $^{\mathrm{nat}}\mathrm{LaCl}_{3}$ sample. The total section radiative $^{139}\mathrm{La}$ sum experimentally observed directly feed ground state was be ${\ensuremath{\sigma}}_{0}^{\mathrm{expt}}=8.58(50)$ b. To assess completeness decay scheme as consistency check, transitions feeding levels below critical energy ${E}_{c}=285$ keV combined with modeled contribution accounting ground-state quasicontinuum arrive ${\ensuremath{\sigma}}_{0}=9.36(74)$ In addition, neutron-separation ${S}_{n}=5161.001(21)$ least-squares fit primary energies low-lying scheme. Furthermore, several nuclear structure improvements are proposed cross-section separation-energy results comparable earlier measurements these quantities.