AsianScientist (Sep. 29, 2014) – An international team of researchers have created a chemical bond between a superheavy element (seaborgium, Sg) and a carbon atom for the first time. This milestone achievement paves the way for the study of the chemical behavior other superheavy elements at the end of the periodic table, where the influence of relativity on chemical properties is most pronounced. This research has been published in Science.

Chemical experiments with superheavy elements—with atomic number beyond 104—are most challenging: First, the very element to be studied has to be artificially created using a particle accelerator. Second, the atoms decay quickly through radioactive processes—in the present case within about 10 seconds, adding to the experiment’s complexity.

A strong motivation for such demanding studies, however, is that the very many positively charged protons inside the atomic nuclei accelerate electrons in the atom’s shells to very high velocities, about 80 percent of the speed of light. At these speeds, relativistic quantum mechanics are required to describe the atoms and molecules.

Chemical studies with superheavy elements often focus on compounds containing halogens and oxygen. However, in such compounds, all of the outermost electrons are occupied in covalent chemical bonds, which may mask relativistic effects. In contrast, superheavy elements bound to carbon atoms have been theoretically predicted to be stable and yet retain the properties suitable for studying relativistic effects.

The Superheavy Element Group at the RIKEN Nishina Center for Accelerator-based Research optimized the seaborgium production in the fusion process of a neon beam (element 10) with a curium target (element 96) and isolated it in the GAs-filled Recoil Ion Separator (GARIS).

Dr. Hiromitsu Haba, team leader at RIKEN, explains: “In the conventional technique for producing superheavy elements, large amounts of byproducts often disturb the detection of single atoms of superheavy elements such as seaborgium. Using the GARIS separator, we were able at last to catch the signals of seaborgium and evaluate its production rates and decay properties. With GARIS, seaborgium became ready for next-generation chemical studies.”

In two weeks of round-the-clock experiments, 18 seaborgium atoms weredetected. The seaborgium atoms were then converted into seaborgium hexacarbonyl complexes, which include six carbon monoxide molecules bound to the seaborgium.

The researchers studied the gaseous properties of the seaborgium hexacarbonyl complexes and found them to be similar to those of the corresponding hexacarbonyls of the homologs molybdenum and tungsten, characteristic compounds of the group-6 elements in the periodic table. The measured properties were in agreement with theoretical calculations, in which the effects of relativity were included.

Prof. Frank Maas, the director of the Helmholtz Institute Mainz (HIM), says “The experiment represents a milestone in chemical studies of superheavy elements, showing that many advanced compounds are within reach of experimental investigation. The perspectives that this opens up for gaining more insight into the nature of chemical bonds, not only in superheavy elements, are fascinating.”

Following this first successful step along the path to more detailed studies of the superheavy elements, the team already has plans for further studies of yet other compounds, and with even heavier elements than seaborgium.

The article can be found at: Even et al. (2014) Synthesis and Detection of a Seaborgium Carbonyl Complex.

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Source: Johannes Gutenberg Universitaet Mainz.

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