The Search for Superheavy Elements

Kratz, J. V.

doi:10.1524/ract.1983.32.13.25

Cited by 42 publications

(12 citation statements)

References 53 publications

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“…7a and 7d and discuss the consequences of both these assumptions concerning the chances to produce surviving superheavy nuclei by fusion reactions between 48Ca projectiles and heavy actinide targets. One of the presently most extensively investigated combination [56] is 48Ca +24SCm leading to element 116 with the neutron (23) and (24) of 0.2 MeV and 13 MeV, respectively. In the latter case, the 13 MeV additional energy needed to fuse drastically reduces the chances to produce surviving superheavy evaporation residues because the excitation energy at the fusion barrier would increase to 39 MeV.…”

Section: Consequences For the Production Of Superheavymentioning

confidence: 99%

Probing sub-barrier fusion and extra-push by measuring fermium evaporation residues in different heavy ion reactions

G�ggeler¹,

Sikkeland²,

Wirth³

et al. 1984

Z Physik A

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The production of fermium isotopes was attempted by complete fusion of different targets and projectiles spanning a wide range of effective entrance channel fissilities below and above the predicted threshold value Xef fthr~(l'/-v... For the most asymmetric systems where fusion is expected to occur without dynamical hindrance we investigate to what extent the expected amount of sub-barrier fusion contributes to the production of fermium evaporation residues. For increasingly symmetric systems the experimental fusion barriers are found to exceed the fusion barriers predicted by the proximity formalism. The barrier heights are discussed in the framework of both the extra-push model and the surface friction model.

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Section: Consequences For the Production Of Superheavymentioning

confidence: 99%

Probing sub-barrier fusion and extra-push by measuring fermium evaporation residues in different heavy ion reactions

G�ggeler¹,

Sikkeland²,

Wirth³

et al. 1984

Z Physik A

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“…With current sensitive methods nuclides like "'Pu can be detected at a level of 10' atoms [4] after chemical Separation from environmental samples. In extreme cases chemical methods have to be applied at a level of a few atoms at a time, e. g., in recent attempts to produce superheavy elements in the laboratory [5], In this context the question arises: Do such extremely small amounts of an element follow its chemical behaviour in macroscopic concentrations, and are Separation procedures worked out at ordinary concentrations applicable at much lower levels? An argument for differences in the behaviour may be the following [6]: Although the behaviour of each individual atom in a Separation step is governed by Statistical rules, the chemistry at macroscopic levels, about 10" atoms and beyond, is very reproducible due to the large number of atoms that undergo the Statistical distribution process involved.…”

Section: Introductionmentioning

confidence: 99%

Chemistry at Low Concentrations: Polonium at a Level of 10⁸ to 10⁵ Atoms

Reischmann¹,

Rumler²,

Trautmann³

et al. 1984

Radiochimica Acta

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Polonium chemistry atlow concentrations/a-spectroscopy/'^'"Po AbstractThe chemical behaviour of polonium was investigated at a level of 10' to 10' atoms per sample using the isotope = 138.38 d). Complete recovery of the polonium was found in electrochemical deposition on silver, electrolysis, coprecipitation with elementary teliurium and with arsenic sulfide, extraction chromatography with tri-n-butylphosphate and cation exchange chromatography.

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“…More recent reviews can be found in Refs. [26,271 and reviews of the heaviest elements recently synthesized in Refs. 128-311.…”

Section: I419mentioning

confidence: 99%

Synthesis of the Heaviest Chemical Elements—Results and Perspectives

Herrmann

1988

Angew. Chem. Int. Ed. Engl.

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Dedicated to Professor Christoph Schmelzer on the occasion of his 80th birthdayAll 17 artificially produced elements heavier than uranium were discovered by nuclearchemical synthesis. The three heaviest ones-elements 107, 108 and 109-were synthesized at the heavy-ion accelerator UNILAC in Darmstadt by nuclear fusion from the heaviest stable nuclei, lead-208 and bismuth-209, and the most neutron-rich stable isotopes of chromium and iron: element 107 from bismuth-209 (atomic number Z=83) and chromium-54 ( Z = 24), element 108 from lead-208 ( Z = 82) and iron-58 ( Z = 26), and element 109 from bismuth-209 and iron-58. The first isotopes detected were those with mass numbers 262 ( Z = 107), 265 ( Z = 108) and 266 ( Z = 109); these nuclei are short-lived a-emitters with halflives of 8.2 ms, 1.8 ms and 3.4 ms, respectively. The yields of these reactions are extremely small; only three atoms of element 109 have ever been observed, Experiments to synthesize element 110 have given ambiguous results. All attempts to detect the "superheavy" elements with proton numbers near Z= 114 and neutron numbers near N = 184 have thus far failed. These elements have been predicted theoretically, and many attempts to synthesize them have been made, e.g. at UNILAC by fusion of calcium-48 (Z=20) with curium-248 (Z=96), or by transference of protons in the collision of two very heavy nuclei such as uranium-238 ( Z = 92). Surprisingly, the heaviest known nuclei are far more stable toward spontaneous fission into two fragments than was expected, but their synthesis is strongly hinderedmuch more than was initially anticipated. It is this hindrance rather than the decreasing nuclear stability which seems to presently limit the extent of the periodic table: even heavier elements should be able to exist, but no way has yet been found to produce them.

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The Search for Superheavy Elements

Cited by 42 publications

References 53 publications

Probing sub-barrier fusion and extra-push by measuring fermium evaporation residues in different heavy ion reactions

Probing sub-barrier fusion and extra-push by measuring fermium evaporation residues in different heavy ion reactions

Chemistry at Low Concentrations: Polonium at a Level of 10⁸ to 10⁵ Atoms

Synthesis of the Heaviest Chemical Elements—Results and Perspectives

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The Search for Superheavy Elements

Cited by 42 publications

References 53 publications

Probing sub-barrier fusion and extra-push by measuring fermium evaporation residues in different heavy ion reactions

Probing sub-barrier fusion and extra-push by measuring fermium evaporation residues in different heavy ion reactions

Chemistry at Low Concentrations: Polonium at a Level of 108 to 105 Atoms

Synthesis of the Heaviest Chemical Elements—Results and Perspectives

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Chemistry at Low Concentrations: Polonium at a Level of 10⁸ to 10⁵ Atoms