Possible Natural Radioactivity of Neodymium

A number of investigators have looked for natural radioactivity in neodymium. All agree that alpha-activity is absent, and most either reported no beta-activity or ascribed the observed activity to common radioactive impurities. However, Libby, who used by far the most sensitive detection method, reported a beta-radiation of maximum energy of about 11 kev and specific activity about 60-120 disintegrations per second per gram. That this activity is truly characteristic of neodymium has been in doubt because Libby did not repurify or fractionate his samples from all other elements to constant specific activity. Takvorian reported inability to detect activity in neodymium, but an inspection of his data shows that his sensitivity was grossly inadequate. A reference by Broda to the unpublished work of Jha (1949) gives no data but implies con6rmation of Libby's findings. A recent report by Curran, Dixon, and Wilson states that Libby's data are probably wrong and that the maximum beta-energy may greatly exceed 11 kev. Finally, the implication is that radiation attributable to the element was observed, but no indication of the level of activity or degree of chemical purification is given.