Neutron capture cross sections of 136,138,140,142Ce and the decays of 137Ce

The activation method has been used to measure the cross sections for radiative capture of neutrons by all isotopes of stable Ce (mass numbers 136, 138, 140, and 142). Both the thermal cross sections and the resonance integrals have been determined from separate irradiations with thermal and epithermal neutrons, wherever possible cross-checking results from different irradiation facilities with different flux distributions. Because determination of precise cross sections by activation requires equally precise values of the decay half-lives, we have remeasured decay half-lives of Ce-137(g), Ce-137(m), Ce-139(m), Ce-141, and Ce-143. Improved values for the energies and intensities of the gamma rays in the decays of Ce-137(g) and Ce-137(m) have also been determined, along with corresponding values for the beta-decay feedings and energies of excited states in La-137.