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"In order to observe the expected increase of stability in full scale, one has to approach as close as possible to the shells Z = 114 and N = 184. It is very hard to synthesize such neutron-rich nuclei in nuclear reactions, since in the fusion of stable nuclei with definite ratio of protons and neutrons, it is impossible to produce the doubly magic nucleus — 298114. Therefore, one has to attempt using nuclei that initially have a maximum neutron number. This was the principal ground of choosing the accelerated ions of 48Ca." "Another aspect of the problem of superheavy elements concerns obtaining even longer-lived elements. In the above-presented experiments, we reached just the edge of the “island” and noticed a steep ascent, but we are far from its peak, where nuclei might live for thousands or maybe millions of years. We lack neutrons in the synthesized nuclei, to approach the shell N = 184. Nowadays it is unreachable—there are no reactions to produce such neutron-rich nuclides. Probably in the far future, physicists will manage to use intense beams of radioactive ions with neutron number more than in 48Ca. Such projects are widely discussed, without considering the costs of constructing those accelerator giants. Yet, one could try a different approach to this problem." Pure Appl. Chem., Vol. 78, No. 5, pp. 889–904, 2006. Yu.Ts. Oganessian "Synthesis and decay properties of superheavy elements"
Abstract from JINR News, 4 March 1999 http://www-cms.llnl.gov/e114/nucphys.html |
The Oganessian et al . collaboration used the reactions 48Ca + 242Pu and 48Ca + 244Pu to make one observed chain, respectively, each originating with 287114 and 289114, respectively, which pass through unknown intermediates and terminate in spontaneous fission. 24494Pu + 4820Ca → 288114Uuq + 4 1n 24494Pu + 4820Ca → 289114Uuq + 3 1n
Yu. Ts. Oganessian, V. K. Utyonkov, Yu. V. Lobanov, F. Sh. Abdullin, A. N. Polyakov, I. V. Shirokovsky, Yu. S. Tsyganov, G. G. Gulbekian, S. L. Bogomolov, B. N. Gikal, A. N. Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov, O. V. Ivanov, G. V. Buklanov, K. Subotic, M. G. Itkis, K. J. Moody, J. F. Wild, N. J. Stoyer, M. A. Stoyer, R. W. Lougheed. Synthesis of supereavy nuclei in the 48 Ca + 244 Pu reaction: 288 114, Phys. Rev. C 62, 041604/1041604/4 (2000). Yu. Ts. Oganessian, V. K. Utyonkov, Yu. V. Lobanov, F. Sh. Abdullin, A. N. Polyakov,I. V. Shirokovsky, Yu. S. Tsyganov, G. G. Gulbekian, S. L. Bogomolov, B. N. Gikal, A. N. Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov, O. V. Ivanov, G. V. Buklanov, K. Subotic, M. G. Itkis, K. J. Moody, J. F. Wild, N. J. Stoyer, M. A. Stoyer, R. W. Lougheed, Synthesis of heavy nuclei in48 Ca + 244 Pu interactions, Phys. Atom. Nucl. 63, 16791687 (2000). From 48 Ca + 244 Pu, two chains originating with 288 114 end in spontaneous fission of 280 Ds after passing through observed intermediate 284 112. Additionally, from 48Ca + 248Cm, one chain ending in spontaneous fission of 280Ds passes through observed intermediate 288 114.
The Oganessian et al . collaborations in which 248Cm or 244Pu + 48Ca are used to produce decay chains commencing with 292 116 or 288 114, respectively, followed by a pair of well-reproduced a -decays assigned to the otherwise unknown 288 114 and 284 112 and terminating in spontaneous fission of previously unknown 280 Ds. The decay energies and lifetimes of three events for 288 114 are internally redundant, but no link to recognized nuclei occurs. In the 244 Pu + 48 Ca study, one chain originating with 289114 followed by a chain observed through 285112 and 281 Ds terminates with spontaneous fission at 277 Hs, all previously unknown. The Dubna collaborations have performed careful, high-quality studies whose acknowledgement as discoveries is unfortunately not yet warranted because of unsecured connection to known descendents or of no observed elemental signatures (such as well-resolved X-ray energies).
For completeness, we note the Ninov et al . Berkeley collaboration report on the reaction 86 Kr + 208Pb leading to observation of three chains terminating in 269Sg that pass through observed intermediate 285 114. Retraction of results appear in : V. Ninov, K. E. Gregorich, W. Loveland, A. Ghiorso, D. C. Hoffman, D. M. Lee, H. Nitsche, W. J. Swiatecki, U. W. Kirbach, C. A. Laue, J. L. Adams, J. B. Patin, D. A. Shaughnessy, D. A. Strellis, P. A. Wilk. Editorial note: Observation of superheavy nuclei produced in the reaction of 86Kr with 208Pb [ Phys. Rev. Lett. 83, 1104 (1999)], Phys. Rev. Lett. 89, 039901 (2002). V. Ninov, K. E. Gregorich, W. Loveland, A. Ghiorso, D. C. Hoffman, D. M. Lee, H. Nitsche, W. J. Swiatecki, U. W. Kirbach, C. A. Laue, J. L. Adams, J. B. Patin, D. A. Shaughnessy, D. A. Strellis, P. A. Wilk. Observation of superheavy nuclei produced in the reaction of Kr86 with Pb208, Phys. Rev. Lett. 83, 11041107 (1999).
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| APSIDIUM | Created: | 2002-09-01 |  114.pdf | ||
| Page update: | 2008-01-11 |
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