The properties of the heaviest element studied to date have been measured

An international research team has succeeded in gaining new insights into the chemical properties of the super-heavy element flerovium – element 114 – at the accelerator facilities at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt. Measurements show that flerovium is the most volatile metal in the periodic table. Flerovium is the heaviest chemically studied element on the periodic table. With the results published in the journal Frontiers in Chemistry, GSI confirms its leading position in the study of the chemistry of superheavy elements and opens new avenues for the International FAIR (Facility for Proton and Ion Research), currently under construction.

Under the leadership of groups from Darmstadt and Mainz, two of the currently known long-lived isotopes of fervium, flerovium-288 and flerovium-289, were produced with the help of the GSI/FAIR accelerator facilities and were chemically analyzed in the TASCA experimental setup. In the periodic table, fluorovium is lower than the heavy metal lead. However, early predictions assumed that the relativistic effects of the high charge in the heavy element core on the valence electrons lead to noble gas-like behaviour, while recent predictions suggested weak metallic behaviour. Two chemical experiments previously performed, one in 2009 at GSI in Darmstadt, led to contradictory interpretations. While the three atoms observed in the first experiment indicated a noble gas-like behavior, the data obtained in the GSI indicated the metallic character based on two atoms. The two experiments could not unambiguously define the character. The new results show that, as expected, flerovium is inert, but capable of forming stronger chemical bonds than the noble gases under the right conditions. Thus Flerovium is the most volatile metal in the periodic table.

Thus Flerovium is the heaviest chemical element whose character has been experimentally verified. By defining chemical properties, GSI/FAIR confirms its leading position in the search for superheavy elements. “Searching at the limits of the periodic table has been a pillar of the research program at GSI from the beginning and will also be in FAIR in the future. The fact that the first basic chemical properties can be searched using just as few atoms and thus Professor Paolo Gioblino, Scientific Director of GSI and FAIR, explains that Giving an indication of how larger quantities of these substances will behave, it is remarkable and thanks to a strong accelerator facility and global collaboration expertise. “With FAIR we bring the universe to the lab and examine the limits of matter, including the chemical elements.”

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Six weeks into the trial process

Experiments conducted at GSI/FAIR to elucidate the chemical character of fluorovium lasted a total of six weeks. To do this, four trillion calcium-48 ions were accelerated every second to ten percent the speed of light by the GSI UNILAC linear accelerator and shot at a target with plutonium-244, creating a few fluorovium atoms per day.

The flerovium atoms formed from the target into the gas-filled TASCA recoil separator. In its magnetic field, the formed isotopes Flerovium-288 and Flerovium-289, which have a life of about one second, were separated from the condensed calcium ion beam and from the byproducts of the nuclear reaction, channeling them through a thin wafer to the stop of the chemical device and stored in a helium/gas mixture argon. The gas mixture transferred the atoms to a COMPACT gas chromatograph, where they first came into contact with the quartz surfaces. If the bonding with quartz is very weak, the atoms are transferred more on the surfaces of gold – first those that are kept at room temperature, and then on the surfaces increasingly cooler to about -160 ° C. The surfaces were applied as a thin coating on special devices to detect nuclear radiation. The detection of individual atoms was performed by spatial detection of radioactive decay. Since the decay products radioactively decay even after a short lifetime, each atom leaves behind a characteristic signature of several events, from which the presence of a flerovium atom can be unambiguously deduced.

One atom per week for chemistry

“Thanks to the combination of the TASCA separator, chemical separation and radioactive decay detection as well as the technical advances of the gas chromatograph since the first experiment, it has been possible to increase the efficiency and reduce the time required for chemical separation to the point where we can observe a flerovium atom every week,” explains Dr. Alexander Yakushev from GSI / FAIR, spokesperson for the international cooperation on trials.

Six decay chains were found in the data analysis. Since the structure is similar to that of the first GSI experiment, the newly acquired data can be combined with the two atoms observed at that time and analyzed together. None of the decay chains appeared in the quartz-coated detector region, indicating that fluorovium is not significantly associated with quartz. Instead, they were all gassed to the gold-plated part of the device in less than a tenth of a second. The eight events form two regions: the first is in the surface region of the gold at room temperature, and the second is in the final part of the chromatograph, at temperatures so low that a very thin layer of ice covered the gold, so that the gold is absorbed and occurred on the ice.

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From the experiments conducted on the atoms of lead, mercury and radon, which were representative of heavy metals, weakly reactive metals and noble gases, it was known that lead forms a strong bond with quartz, while mercury reaches the gold detector. At room temperature, radon flies over the first part of the gold detector and is only partially captured at the lowest temperatures. Flerovium results can be compared with this behavior.

Apparently, two modes of interaction of Flerovium species with the gold surface are observed. Deposition on gold at room temperature indicates the formation of a relatively strong chemical bond, which does not occur with noble gases. On the other hand, it seems that some atoms never had the opportunity to form such bonds and were transported long distances across the surface of the gold, all the way to the lowest temperatures. This detector area is a trap for all kinds of items. This complex behavior can be explained by the morphology of the surface of the gold: it consists of small gold clusters, at their boundaries there are highly reactive sites, apparently allowing the fluorovium to bind. The ability of some flerovium atoms to reach the cold zone indicates that only atoms that collided with such spots were bound, unlike mercury, which was certainly retained on gold. This means that the chemical reaction of fluorovium is weaker than that of volatile metallic mercury. The present data cannot completely exclude that the first region of gold precipitation at room temperature is caused by the formation of fluorovium particles. From this hypothesis also, it follows that fervium is more chemically reactive than the inert gas element.

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International and multidisciplinary cooperation as a key to understanding

The exotic plutonium target material used to produce fluorovium was provided in part by Lawrence Livermore National Laboratory (LLNL), USA. At the Department of Chemistry at the TRIGA site of Johannes Gutenberg Mainz University (JGU), the material was electrostatically deposited on thin film titanium flakes manufactured in GSI/FAIR. Dr. says. Don Shaunessy, chair of nuclear and chemical sciences at LLNL. “This international collaboration brings together skills and expertise from around the world to solve challenging scientific problems and answer long-standing questions, such as the chemical properties of fluorovium.”

“Our accelerator experiment was complemented by a detailed investigation of the detector surface in collaboration with several departments of GSI as well as the Department of Chemistry and the Institute of Physics at JGU. This has been shown to be key to understanding the chemical character of fluorovium. This means that the data from the two previous experiments are now well understood and congruent. With our new findings,” says Christoph Dollmann, Professor of Nuclear Chemistry at JGU and Chair of Working Groups at GSI and at Helmholtz Institute Mainz (HIM), the collaboration between GSI and JGU.

How do relativistic influences affect its neighbors, the elements nihonium (element 113) and moscovium (element 115), which have only been officially recognized in recent years, are the subject of the following experiments. The first data was already obtained as part of the FAIR Phase 0 program at GSI. The researchers also expect more stable isotopes of fluorovium, but they have not yet been found. However, researchers already know that they can expect a metallic element.

In addition to GSI/FAIR and JGU, the experiment also included HIM, University of Liverpool (UK), Lund University (Sweden), University of Jyväskyla (Finland), University of Oslo (Norway), Institute of Electron Technology (Poland) and Lawrence Livermore National Laboratory (US USA), Saha Institute of Nuclear Physics, Indian Institute of Technology Rorke (India), Joint Atomic Energy Agency, RIKEN Research Center (Japan) and Australian National University Center (Australia).

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