The parent of actinium

Abstract

It has been recognised for more than a decade that actinium cannot be a primary radio-element, but hitherto all attem pts to obtain evidence of its continuous production, in the same way as has been established for polonium and for radium, have m et with no success. As our knowledge of radioactive change has become precise, the conceivable modes in which actinium could originate have been narrowed down and, one by one, experimentally elimi nated without the parent of actinium having been discovered.In the present paper an account is given of experiments which have been successful in separating from uranium minerals preparations initially free from actinium but producing that elem ent in the course of years. In 1913, a minute production of actinium, almost too small to be confident of, was recorded by one of us in the old preparations of uranium-X separated from 50 kgrm. of uranyl nitrate in 1909.* The subsequent history of these preparations has confirmed this minute growth, and placed it beyond all doubt, although even now, after eight years, it is still very small in comparison with the growth in the later preparations separated from uranium minerals.Before dealing with the newer experiments, the opportunity will be taken of giving a fairly full account of the long and involved history of the problem, and of correlating and bringing up to date the evidence that can be derived from these old uranium-X preparations.The experiments were undertaken when the course of the disintegration of uranium and its connec tion with radium was quite obscure, but the experiments afford valuable data, which has never been properly discussed in the light of recent discoveries, on the possible modes of origin of actinium.W ith regard to the new work, in the absence of one of us on military service since 1915, the experiments were continued for a time by Miss Ada Hitchens, B.Sc., Carnegie Research Scholar, until she also left to engage in war duties.Her valuable assistance has contributed very materially to the definiteness of the conclusions that it has been possible to arrive at.H istory o f the Problem.Although discovered in 1899, by Debierne, actinium still remains probably the least known of all the radio-elements. The statement does not apply to

Double photoexcitation involving2pand4felectrons inL3-edge x-ray absor

“…The enrichment of Pa has been used to determine the age of marine sediments. 14 19 The primary decay mode of 231 Pa and lighter isotopes is a decay to actinium isotopes, whereas the heavier Pa isotopes undergo a ␤ − decay to uranium isotopes. Protactinium is related to an extraordinary chemistry due to its position at the beginning of the actinide series, whose chemical properties depend on the delocalized 5f and 6d electron configuration.…”

Protactinium

“…This suggested that Ac was being produced from UX 'through an intermediate substance'. Five years later Soddy and Cranston (1918) [see also Sackett (1960)] had confirmed the growth beyond doubt and had separated the parent of Ac by sublimation from pitchblende in a current of air containing CCl 4 at incipient red heat. This method was later applied by Fried (1950, 1959) to the separation of 233 Pa from neutron-irradiated 232 Th.…”

Exploring the boundaries of the nuclear landscape: α -decay properties of Pa211

“…The element 91, initially referred as UrX 2 , was discovered in 1913 by Fajans and Göhring via observation of 234 Pa [21], followed by the independent discovery of 231 Pa by Soddy and Cranston 2 [23] and Hahn and Meitner [24] in 1918, of which the latter initiated the name protactinium [25]. To date, 28 protactinium isotopes, with a mass number ranging from 212 to 239, have been rigorously identified [2,25].…”