Artificial Radioactivity of Dysprosium and other Rare Earth Elements

Abstract

IN their pioneer work on artificial radioactivity through neutron bombardment, Fermi and his collaborators announced the discovery of the activity of some of the rare earth elements, namely, of lanthanum, praseodymium, neodymium, samarium and gadolinium. Recently, Sugden¹ found that terbium shows an appreciable, and europium a very strong, radioactivity after bombardment with neutrons. We find that dysprosium shows an unusually strong activity due to ₆₆Dy¹⁶⁵ under the action of slow neutrons; so far as we can ascertain, it is the strongest activity found hitherto. So little as 1/100 mgm. of dysprosium gives an easily detectable radioactivity after bombardment with neutrons from a source containing a few hundred millicuries of radium emanation.