These new developments are contrary to the assumption made in the semiempirical shellmodel mass equation (SSME) [12] (see also ref. [13]) that Z = 114 is the next proton magic number beyond lead. The equation stops at Z = 114, and it is unsuitable for extrapolation already earlier, beyond Hs (Z = 108), as shown by its increasing deviations from the data beyond that (like in fig. 4 of ref. [1]). One has to find an appropriate substitute for the equation in the neighbourhood of Z = 114 and beyond.During the early stages of the SSME [14], when it was adjusted separately in individual shell regions in the N − Z plane, both Z = 114 and Z = 126, which were at the time considered possible candidates for the post-lead proton magic number, were tried as a shell region boundary in each of the two heaviest regions with Z ≥ 82 and respective N boundaries 82 ≤ N ≤ 126 (called here region A) and 126 ≤ N ≤184 (called region B).

Evidence for the existence of long-lived neutron-deficient isotopes has been found in a study of naturally-occurring Th using inductively coupled plasma-sector field mass spectrometry. They are interpreted as belonging to the recently discovered class of long-lived high spin super-and hyperdeformed isomers.In recent years, long-lived high spin super-and hyperdeformed isomeric states with unusual radioactive decay properties have been discovered in heavy and very heavy nuclei [1][2][3][4] . This discovery motivated us to perform a search for naturally-occurring long-lived isomeric states. (Up to now there is only one such isomeric state known, namely the 75.3 keV excited state in 180 Ta with a half-life of >1.2x10 15 y (ref. 5 )). Madagascan monazite and commercially available Th and U standard solutions were studied using different mass spectrometers, including an accelerator mass spectrometer. In the present paper we present the results obtained with pure Th standard solutions and also in one case with a monazite digest solution, using inductively coupled plasma-sector field mass spectrometer (ICP-SFMS).The instrument was an Element2 (Thermo-Electron, Bremen, Germany). The predefined medium resolution mode of m/∆m = 4000 (10% valley definition) was used throughout the experiments so as to separate atomic ions from interfering molecular ions with the same mass number. The sensitivityenhanced setup of the instrument was similar to that described in Ref.6 where a capacitive decoupling system and high-performance "X" skimmer were used, providing sensitivity for 232 16 O + peaks. Two 1000 mg l -1 Th stock solutions "A" and "B" from two manufacturers, Inorganic Venture and Customer Grade, were obtained from LGC Promochem AB (Borås, Sweden). Complete elemental screening was performed on both solutions to assess the impurity concentration levels PDF created with pdfFactory trial version www.pdffactory.com 2 The solutions were analyzed during three separate sessions: May 25, October 5, and November 6, 2005. A range of about 0.2 mass unit was scanned in each measured spectrum. This range was divided into approximately 60 channels. During the first session, masses from 210 to 269 were analyzed with an integration time per channel of 0.6 sec. During the second and third sessions, selected mass regions (where some indication of unidentified signals had been detected) were measured using an integration time per channel of 3 and 12 sec, respectively. Instrumental sensitivity varied significantly among runs as a result of matrix effects caused by the introduction of highly concentrated solutions into the ICP source. During the first session, the monazite digest (1000 mg monazite l -1 ) and Th solution A (diluted to 20 mg Th l -1 ) were scanned once. (The Th content in the monazite was approximately 2%. The contents of typical rare earth elements in it, like Ce, Dy and Er, were about 5%, 0.05% and 0.02%, respectively.) During the second session, 20 mg l -1 of Th A and B solutions spiked with 2 µg l -1 Bi were studied and eac...

A study has been made of the internal fields acting on Fe 57 nuclei in some spinel ferrites, with particular reference to the low-temperature order-disorder transition in magnetite, using the techniques of Mossbauer absorption. For the Fe 3+ ions at both the octahedral and tetrahedral sites in nickel ferrite (NiFe 2 0 4 ) at 300°K, 7Fe20 3 at 85° and 300°K, and magnetite (Fe30 4 ) at 85 °K, the effective magnetic field at the Fe 67 nuclei is the same and equal to about 5.1 XlO 5 oe. In magnetite, the value of H e u in the Fe 2+ ions is about 4.5X10 5 oe at 85°K. Measurements on Fe 3 04 at room temperatures provide a microscopic confirmation of Verwey's hypothesis that above the transition temperature of magnetite there is a fast exchange between the ferrous and ferric ions in the octahedral sites.

Evidence for the existence of long-lived isotopes with atomic mass numbers 261 and 265 and abundance of (1-10)x10 −10 relative to Au has been found in a study of natural Au using an inductively coupled plasma -sector field mass spectrometer. The measured masses fit the predictions made for the masses of 261 Rg and 265 Rg (Z=111) and for some isotopes of nearby elements. The possibility that these isotopes belong to the recently discovered class of long-lived high spin superand hyperdeformed isomeric states is discussed.

Unidentified low energy and very enhanced α-particle groups have been observed in various actinide fractions produced via secondary reactions in a CERN W target which had been irradiated with 24-GeV protons. In particular, 5.14, 5.27 and 5.53 MeV α-particle groups with corresponding half-lives of 3.8 ± 1.0 y, 625 ± 84 d and 26 ± 7 d, have been seen in Bk, Es and Lr-No sources, respectively. The measured energies are a few MeV lower than the known ground state to ground state α-decays in the corresponding neutron-deficient actinide nuclei. The half-lives are 10 4 to 10 7 shorter than expected from energy versus lifetime relationship for such low-energy α-particles in this region of nuclei. The deduced evaporation residue cross sections are in the mb region, about 10 4 times higher than expected. Not only is it impossible to identify these αdecays with any known activity in the whole nuclear chart, but they also could not be due to hypothetically unknown isomeric states in various conceivable neutron deficient nuclei, nor due to unknown isomeric states in the rare-earth region. Based on the fact that in other experiments we have found isomeric states in the second and third minima of the potential for other heavy ion reaction products, one can now understand in a quantitative way, both the unusual low energies, the unusual enhanced lifetimes and the unusual large production cross sections, in terms of production of similar isomeric states in appropriate actinide isotopes. Some consequences regarding the production of the long-lived superheavy elements are also discussed. Int. J. Mod. Phys. E 2001.10:209-236. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ DAVIS on 02/05/15. For personal use only.