The Expanding Periodic Table: New Discoveries and Chemistry of the Heaviest Elements

ChEMS Seminar

Featuring: Dr. Heino Nitsche

Professor, Department of Chemistry

Faculty Senior Scientist, Lawrence Berkeley National Laboratory

University of California, Berkeley

During the last decade, six new elements (113, 114, 115, 116, 117, and 118) and 52 new isotopes with relatively long decay half-lives have been reported .  The production of these so called super-heavy elements was achieved via nuclear reactions of calcium-48 ion beams and actinide targets.  These reactions appear to occur with surprisingly “large” and constant cross sections, on the order of picobarns.  Using the Berkeley Gas-Filled Separator (BGS) at the Lawrence Berkeley National Laboratory in early 2009, we independently verified these results for the production of element 114.

We also actively participated in experiments to provide further confirmation of superheavy element formation with the newly completed TASCA gas-filled separator at GSI, Germany.  In these experiments, the 48Ca + 244Pu reaction was used to produce more neutron-rich isotopes of element 114 via the ²⁴⁴Pu (⁴⁸Ca,4n)²⁸⁸114 and ²⁴⁴Pu(⁴⁸Ca,3n)²⁸⁹114 reactions.  Several atoms each of ²⁸⁸114 and ²⁸⁹114 were produced.  Decay modes, decay energies, half-lives and production cross sections agree with those published by the Dubna group.  This additional superheavy element confirmation experiment reinforces the conclusion:  superheavy elements are real, and can be produced at rates of atoms per week.

In 2010, we produced a new, neutron-deficient element 114 isotope, ²⁸⁵114, using the ⁴⁸Ca + ²⁴²Pu → ²⁸⁵114 + 5n reaction with the BGS.  The decay of ²⁸⁵114 and daughters led to the identification of six new isotopes:  ²⁸⁵114, ²⁸¹Cn, ²⁷⁷Ds, ²⁷³Hs, ²⁶⁹Sg, and ²⁶⁵Rf.  We also observed the decay of ²⁸⁶114 via the ⁴⁸Ca +²⁴²Pu → ²⁸⁶114 + 4n reaction, thus re-confirming earlier work, both at the BGS and at Dubna.

This talk will discuss the recent discoveries and selected verification experiments of the new elements. First one-atom-at-a time chemistry experiments with the heaviest elements will also be discussed.

Biography:

Dr. Nitsche received his BS degree (Dipl. Chem.) in chemistry (1976) and PhD degree (Dr. rer. nat.) in nuclear and radiochemistry (1980) from the Freie Universität in Berlin, Germany.  Nitsche’s research interests include nuclear chemistry and physics of the heaviest elements, fundamental molecular-level understanding of actinides at metal-oxide and biological interfaces, the thermodynamics and kinetics of actinides in solution and their relation to nuclear-waste disposal, environmental contamination, and separation science.