World news – Discoveries at the Edge of the Periodic Table: First Measurements of Einsteinium

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February 3, 2021

by Lawrence Berkeley National Laboratory

Since Element 99 – Einsteinium – was discovered in 1952 at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) from the rubble of the first hydrogen bomb, scientists have done very few experiments with it because it is so difficult to make and unusually radioactive . A team of chemists at Berkeley Lab overcame these barriers to report the first study that characterizes some of its properties and opens the door to a better understanding of the remaining transuranic elements of the actinide series.

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The study « Structural and Spectroscopic Characterization of an Einsteinium Complex », published in the journal Nature, was jointly led by Berkeley Lab scientist Rebecca Abergel and Los Alamos National Laboratory scientist Stosh Kozimor, and included scientists from both UC laboratories Berkeley. and Georgetown University, some of which are PhD and postdoc. At less than 250 nanograms of the element, the team measured the first Einsteinium bond distance, a fundamental property of an element’s interactions with other atoms and molecules.

« Not much is known about Einsteinium, » said Abergel, who works at Heavy Element Chemistry -Group at Berkeley Lab and is an assistant professor in the Nuclear Engineering Department at UC Berkeley. « It is a remarkable achievement that we have been able to work with this small amount of material and do inorganic chemistry. It matters because the more we know about chemical behavior, the more we can use that understanding to develop new materials or new ones Applying technology, not necessarily just with Einsteinium, but also with the rest of the actinides. And we can see trends in the periodic table. « 

Abergel and her team first used experimental facilities that weren’t available decades ago as the Einsteinium was discovered – the Molecular Foundry at Berkeley Lab and the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC National Accelerator Laboratory, both user facilities of the DOE Office of Science – to perform luminescence spectroscopy and X-ray absorption spectroscopy experiments.

But at first it was almost half the battle in getting the sample into a usable form. « This whole newspaper is a long series of unfortunate events, » she said dryly.

The material was made in the High Flux Isotope Reactor at Oak Ridge National Laboratory, one of the few places in the world where Einsteinium can be made. This involves bombarding Curium targets with neutrons to trigger a long chain of nuclear reactions. The first problem they encountered was that the sample was contaminated with a significant amount of calcium, as producing pure Einsteinium in a usable amount is extraordinarily difficult.

Hence, they had their original plan for using it abandon x-ray crystallography – which is considered the gold standard for obtaining structural information about highly radioactive molecules, but which requires a pure metal sample – and instead develop a new method of sample preparation and leverage element-specific research techniques. Los Alamos researchers were instrumental in this step by designing a sample holder specifically designed for the challenges of Einsteinium.

Then the fight against radioactive decay was another challenge. The Berkeley Lab team conducted their experiments with Einsteinium-254, one of the more stable isotopes of the element. It has a half-life of 276 days, which is the time it takes half the material to break down. Although the team was able to conduct many of the experiments prior to the coronavirus pandemic, it had plans for follow-up experiments that were suspended due to pandemic shutdowns. When they were able to return to their laboratory last summer, most of the sample was gone.

Nevertheless, the researchers were able to measure a bond distance with Einsteinium and also discovered a physico-chemical behavior that differs from what is Actinide series would be expected, which are the elements in the bottom row of the periodic table.

« Determining the bond distance may not sound interesting, but it’s the first thing you want to know about how a metal connects to other molecules What chemical interaction will this element have with other atoms and molecules?  » Abergel said.

Once scientists have this picture of the atomic arrangement of a molecule with einsteinium, they can try to find interesting chemical properties and better understand periodic trends. « By getting this data, we can get a better and more complete understanding of the behavior of the entire actinide series. In this series we have elements or isotopes that are useful for making nuclear power or radiopharmaceuticals, » she said.

Interestingly, this one offers Research also gives you the opportunity to explore what is beyond the periodic table and possibly discover a new element. « We’re really starting to understand a little better what’s going on towards the end of the periodic table, and next one could also imagine an Einsteinium target to discover new elements, » said Abergel. « Similar to the newest elements discovered in the past 10 years, like Tennessine, which used a Berkelium target, if you were able to isolate enough pure Einsteinium to make a target, you could , looking for other elements and getting closer to the (theorized) island of stability, « where nuclear physicists have predicted that isotopes could have half-lives of minutes or even days rather than the microseconds or less half-lives common in the superheavy elements.

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Ref: https://phys.org

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