Determination of the 151Eu(n,γ) 152m1,gEu and 153Eu(n,γ) 154Eu Reaction Cross Sections at Thermal Neutron Energy

We have measured partial gamma-ray cross sections following neutron capture in enriched Eu-151 and Eu-153 targets at the cold-neutron-beam facility of the Budapest Research Reactor. The cross sections were standardized using a stoichiometric (EuCl3)-Eu-nat target with the well-known 1951-keV gamma-ray cross section from the Cl-35(n,gamma) Cl-36 reaction at the cold-neutron-beam facility of the Garching Research Reactor. The gamma-ray cross sections were corrected for effective g-factors. These data were combined with the structural information of Eu-152 and Eu-154 given in the Evaluated Nuclear Structure Data File to produce capture gamma-ray level schemes. The total radiative capture cross sections of the Eu-151(n,gamma) Eu-152m1,Eu- g and Eu-153(n,gamma) 154 Eu reactions were determined by summing the experimental transition intensities from known levels with simulated intensities of transitions from higher excitations to the ground- or metastable-state. The individual Eu-151(n,gamma) Eu-152m1 and Eu-151(n,gamma) Eu-152g reaction cross sections disagree with values in the literature. However, the total cross section of the Eu-151(n,gamma) Eu-152 reaction does agree with those values. Also, our deduced cross section for the Eu-153(n,gamma) Eu-154 reaction closely follows the data in the literature. These results are supported by an earlier standardization experiment done at the Budapest Research Reactor using a target of Eu2O3 solution in H2SO4.