EVIDENCE FOR THE POSSIBLE EXISTENCE OF A LONG-LIVED SUPERHEAVY NUCLEUS WITH ATOMIC MASS NUMBER A = 292 AND ATOMIC NUMBER Z ≅ 122 IN NATURAL Th

Abstract

Evidence for the existence of a superheavy nucleus with atomic mass number A=292 and abundance (1-10)x10 -12 relative to 232 Th has been found in a study of natural Th using inductively coupled plasma-sector field mass spectrometry. The measured mass matches the predictions 1,2 for the mass of an isotope with atomic number Z=122 or a nearby element. Its estimated half-life of t 1/2 ≥10 8 y suggests that a long-lived isomeric state exists in this isotope. The possibility that it might belong to a new class of long-lived high spin super-and hyperdeformed isomeric states is discussed. 3-6The question "how heavy can a nucleus be" is a fundamental problem in nuclear physics. The mass M A of an atom is equal to:where M H and M n are the masses of the hydrogen atom and the neutron, respectively, and BE is the binding energy of the nucleus. The binding energy per nucleon (BE/u) of stable nuclei has a broad maximum around A ≈ 60, with a value of 8.7 MeV/u, which falls monotonically to about 7.6 MeV/u at Th and U. 19 The predicted BE/u values for the superactinide nuclei are around 6.9 MeV/u. 1,2,20,21 Therefore, masses of superactinide isotopes are higher than, and resolvable from, the masses of all molecules with the same mass number, except for multihydrogen-containing molecules. This is seen in Fig. 1 In principle, natural minerals like monazite, which is the usual source material for Th, would be the most promising materials to study. However, background was the main obstacle when looking for isotopes with relative abundance of (1-10)x10 -11 in natural materials. 10Therefore, purified natural Th was used in our measurements.In the present work, we performed accurate mass measurements for masses 287 to 294 in Th solutions. Evidence was obtained for the existence of an isotope with a mass that matches the predictions for atomic mass number 292 and Z around 122. Here we describe this observation.The experimental procedure was similar to that described earlier. 10 Inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) was used for the experiments. The ICP-SFMS is an Element2 (Finnigan, Thermo-Electron, Bremen, Germany). In this instrument, a solution of the material to be studied is introduced into a high temperature (6000-8000 K) plasma source. At these temperatures, predominantly atomic species are present. Molecular ions are produced after the source, mainly by interaction with oxygen and hydrogen ions from the solution. The predefined medium resolution mode, m/∆m = 4000 (10% valley definition), was used throughout to separate atomic ions from molecules with the same mass number. The sensitivity-enhanced set-up of the instrument was similar to that described in Ref. During the first session, masses from 287 to 294 were analysed using the Th solutions with an integration time of 1 s channel -1 , and these measurements were made three to five times each. In one spectrum, two events were observed with a solution produced by CustomerGrade (from LGC Promochem AB, Borås, Sweden) at a mass that fits the predic...

Icp-SFMS Search for Long-Lived Naturally-Occurring Heavy, Superheavy and Superactinide Nuclei Compared to Ams Experiments

“…We argue that it may not be surprising that results obtained from small random samplings of inhomogeneous natural minerals would contrast with concentrations found in homogeneous materials extracted from large quantities of ore. We also point out that it is possible that the groups of counts at masses 296 and 294 seen by Dellinger et al could be, within experimental uncertainties, due to Another comment we would like to make is related to the conclusion of Dellinger et al that based on their results, there are no naturally-occurring SHEs. In addition to what was mentioned above [4][5][6][7] and also in [9], it seems to us that even their results could indicate the contrary. We refer in particular to Fig.…”

“…(However see below.) As for ThO 2 , we do not think, that based on a single measurement using a very complicated system, one can conclude that all our measurements [4][5][6][7] done with the relatively straightforward ICP-SFMS system are artifacts. It would be more convincing to point out a weakness in our measurements, which neither we nor Dellinger et al [1][2][3] have been able to find.…”

“…−12 relative to 232 Th) [7]. An important difference between our works [4][5][6][7] and those of Dellinger et al [1][2][3] is that we used processed Au and Th starting materials, and Dellinger et al, except for a few cases, used raw minerals.…”

“…An important difference between our works [4][5][6][7] and those of Dellinger et al [1][2][3] is that we used processed Au and Th starting materials, and Dellinger et al, except for a few cases, used raw minerals. It may not be surprising that results obtained with random samplings of a few mg would contrast with concentrations found in processed homogeneous starting materials which probe a large amount of natural ore.…”

Accelerator mass spectrometry – from DNA to astrophysics

“…However, the group of A. Marinov et al from Jerusalem recently reported positive evidence from highresolution inductively coupled plasma -sector field mass spectrometry (ICP-SF-MS) for long-lived neutrondeficient Th isotopes [29], neutron deficient Rg isotopes in gold [30], and a SHE nuclide with A = 292 and Z ~ 122 in thorium [31]. This triggered extensive AMS experiments at the 14-MV tandem accelerator in Munich [32,33], and at the 3-MV VERA facility in Vienna [34][35][36].…”