Measurements of gamma-ray emission probabilities in the decay of americium-244g

Accurate data of gamma-ray emission probabilities are frequently needed when one quantitatively determines the amount of isotope by gamma-ray measurements or obtains neutron capture cross-sections using them. Americium-243, one of the most important minor actinides, produces Am-244 after neutron capture. The 744-keV gamma-ray decaying from the ground state of Am-244 has a relatively large gamma-ray emission probability about 66%; however, its uncertainty is as large as 29%. The uncertainty of the gamma-ray emission probability leads to a major factor of the systematic uncertainty on determining an amount of isotope, and therefore the gamma-ray emission probability was measured by using an activation method and an examined level structure of Cm-244. In this study, the emission probability of 744-keV gamma-ray was derived as 66.5 +/- 1.1%, and its uncertainty was improved from 29% to 2%.