Photoactivation of Rare Earth Elements with 20 MeV Bremsstrahlung

Abstract

The oxides of scandium, yttrium and all elements from lanthanum through lutetium, except promethium, were irradiated for 1hr with bremsstrahlung γ-rays converted from a 20MeV electron beam, and the radioactive species produced as a result have been examined on the basis of photonuclear reactions, their yields, and their applicability to activation analyses. The sensitivity and selectivity of the proposed method are discussed from the data thus obtained. The (γ,n) reaction was predominant for most elements, and at least 28 product nuclides have been identified. A number of other (γ,2n) reactions have also been observed. The yields of the (γn) reactions have been estimated for the lanthanide rare earths through measurement of the resultant activity to be about 107mole·R and somewhat more than 10% smaller for the corresponding (γ,2n) reaction. Reactions with charged particle emission contributed only a small fraction in the observed radioactivity. Extraneous activity arising from neutron capture was also measured; these activities could be reduced considerably by encasing the sample in boron. The lower limits of detection averaged about 1 μg for most of the rare earth elements.