05.17.16

DOE Isotope Program Provides Target Material for the Discovery of Superheavy Elements

New element 117 and its decay products establish the existence of long-sought Island of Stability.

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The green dot at the bottom of the glass vial is a solution containing 22 milligrams of ultra-pure 249Bk produced at ORNL’s High Flux Isotope Reactor and Radiochemical Engineering Development Center at ORNL.

The Science

Two isotopes of a new element with atomic number Z=117 were created by an international collaboration in the reaction between unique radioactive 249Bk target material produced at ORNL through the DOE Isotope Program and an intense beam of 48Ca ions at the Joint Institute for Nuclear Research (Dubna, Russia). This result completed the 7th row of the Periodic Table of Elements and demonstrated the existence of long-sought Island of Stability for superheavy nuclei, originally proposed by Glenn Seaborg in the 1960s.

The Impact

249Bk target material was provided by the DOE Isotope Program and enabled the experiments which discovered element 117 and subsequent experiments which confirmed its existence, as well as searches for other superheavy elements. The longstanding question of the existence of the Island of Stability for superheavy elements has been answered with the discovery of new nuclei stabilized against radioactive decay. The enhanced stability is a result of quantum effects and related shell structure in these nuclei. It opens up the world of nuclei and atoms to further expansion toward even heavier elements and their structure. Longer half-lives of the isotopes observed in decay chains of these new elements create for the first time an opportunity to measure nuclear masses and to determine chemical properties of superheavy elements, allowing the expansion of knowledge of the behavior of atomic and nuclear matter in new ways. The discovery of element 117 was officially recognized by the Division of Inorganic Chemistry of the International Union of Pure and Applied Chemistry in December 2015.

Summary

New elements and nuclei establishing the existence of the Island of Stability and expanding the Periodic Table of Elements were produced in hot fusion reactions using targets of unique radioactive actinide materials from ORNL including short-lived 249Bk and projectiles of 48Ca of unprecedented intensity at Dubna. These discoveries are the direct result of close collaboration between Russian and U.S. scientists leveraging the unique research capabilities of each nation. This collaboration has enabled the discovery of five new heaviest elements and over fifty new superheavy nuclei at the Island of Stability. The systematic increase in half-lives, over three orders of magnitude across multiple superheavy nuclei as neutron number increases, clearly demonstrates the existence of  a new shell gap enhancing the stability of nuclei as the neutron number N=184 is approached.

Contact

K. P. Rykaczewski and J.B. Roberto
ORNL, 1 Bethel Valley Road, Oak Ridge, TN 37830
rykaczewskik@ornl.gov; robertojb@ornl.gov

Funding

DOE Office of Science, Office of Nuclear Physics, Isotope Development and Production for Research and Applications, and Low-Energy Nuclear Physics Program.

Publications

Yu. Ts. Oganessian, F. Sh.Abdullin, P.D. Bailey, D. E. Benker, M. E. Bennett, S. N. Dmitriev, J. G. Ezold, J. H. Hamilton, R. A. Henderson, M. G. Itkis, Yu. V. Lobanov, A. N. Mezentsev, K. J. Moody, S. L. Nelson, A. N. Polyakov, C. E. Porter, A. V. Ramayya, F. D. Riley, J. B. Roberto, M. A. Ryabinin, K. P. Rykaczewski, R. N. Sagaidak, D. A. Shaughnessy, I. V. Shirokovsky, M. A. Stoyer, V. G. Subbotin, R. Sudowe, A. M. Sukhov, Yu. S. Tsyganov, V. K. Utyonkov, A. A. Voinov, G. K. Vostokin, and P. A. Wilk, “Synthesis of a New Element with Atomic Number Z = 117.” Phys. Rev. Lett. 104, 142502 (2010).

URL: http://dx.doi.org/10.1103/PhysRevLett.104.142502External link

Yu. Ts. Oganessian, F. Sh. Abdullin, P. D. Bailey, D. E. Benker, M. E. Bennett, S. N. Dmitriev, J. G. Ezold, J. H. Hamilton, R. A. Henderson, M. G. Itkis, Yu. V. Lobanov, A. N. Mezentsev, K. J. Moody, S. L. Nelson, A. N. Polyakov, C. E. Porter, A. V. Ramayya, F. D. Riley, J. B. Roberto, M. A. Ryabinin, K. P. Rykaczewski, R. N. Sagaidak, D. A. Shaughnessy, I. V. Shirokovsky, M. A. Stoyer, V. G. Subbotin, R. Sudowe, A. M. Sukhov, R. Taylor, Yu. S. Tsyganov, V. K. Utyonkov, A. A. Voinov, G. K. Vostokin, and P. A. Wilk,  “Eleven new heaviest isotopes of elements Z = 105 to Z = 117 identified among the products of 249Bk+48Ca reactions.” Phys. Rev. C 83, 054315 (2011).

URL: http://dx.doi.org/10.1103/PhysRevC.83.054315External link

Yu. Ts. Oganessian, F. Sh. Abdullin, C. Alexander, J. Binder, R. A. Boll, S. N. Dmitriev, J. Ezold, K. Felker, J. M. Gostic, R. K. Grzywacz, J. H. Hamilton, R. A. Henderson, M. G. Itkis, K. Miernik, D. Miller, K. J. Moody, A. N. Polyakov, A. V. Ramayya, J. B. Roberto, M. A. Ryabinin, K. P. Rykaczewski, R. N. Sagaidak, D. A. Shaughnessy, I. V. Shirokovsky, M. V. Shumeiko, M. A. Stoyer, N. J. Stoyer, V. G. Subbotin, A. M. Sukhov, Yu. S. Tsyganov, V. K. Utyonkov, A. A. Voinov, and G. K. Vostokin, “Production and Decay of the Heaviest Nuclei 293,294117 and 294118.” Phys. Rev. Lett. 109, 162501 (2012).

URL: http://dx.doi.org/10.1103/PhysRevLett.109.162501External link

Yu.Ts. Oganessian, F.Sh. Abdullin, C. Alexander, J. Binder, R.A. Boll, S.N. Dmitriev, J. Ezold, K. Felker, J.M. Gostic, R.K. Grzywacz, J.H. Hamilton, R.A. Henderson, M.G. Itkis, K. Miernik, D. Miller, K.J. Moody, A.N. Polyakov, A.V. Ramayya, J.B. Roberto, M.A. Ryabinin, K.P. Rykaczewski, R.N. Sagaidak, D.A. Shaughnessy, I.V. Shirokovsky, M.V. Shumeiko, M.A. Stoyer, N.J. Stoyer, V.G. Subbotin, A.M. Sukhov, Yu.S. Tsyganov, V.K. Utyonkov, A.A. Voinov, and G.K. Vostokin, "Experimental studies of the 249Bk +48Ca  reaction including decay properties and excitation function for isotopes of element 117 and discovery of the new isotope 277Mt." Phys. Rev. C 87, 054621 (2013).

URL: http://dx.doi.org/10.1103/PhysRevC.87.054621External link

Y.T. Oganessian and K.P. Rykaczewski, “A beachhead on the island of stability.” Physics Today, vol. 68, no.3, p.32 (2015). ISSN 0031-9228.

J.B. Roberto, C. W. Alexander, R.A. Boll, J.D. Burns, J.G. Ezold, L.K. Felker, S.L. Hogle and K.P. Rykaczewski, “Actinide targets for the synthesis of superheavy elements.” Nucl. Phys. A 944, 99 (2015).

URL: http://doi:10.1016/j.nuclphysa.2015.06.009External link

Related Links

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Program: BES, SUF, NP

Performer/Facility: SC User Facilities, BES User Facilities, HFIR

Additional: Collaborations, International Collaboration

Last modified: 12/13/2016 8:11:53 AM