The heavy element einsteinium, first conceived in 1952 on the southern Pacific island of Elugelab, is one of the most important members of the Periodic Table; it does not occur naturally and is so unstable that it is difficult to get long enough of the good to actually study it.
Now a team of chemists at Lawrence Berkeley National Laboratory, Los Alamos National Laboratory and Georgetown University have managed it. They inspected a microscopic amount of einsteinium-254 to better understand the elusive element’s fundamental chemical properties and behavior. Their research is published today in the journal Nature.
Einsteinium is manufactured at the Oak Ridge National Laboratory High Flood Isotope Reactor as a by-product of California-252 biennial production (another heavy, laboratory synthetic element, but one that is commercially usable.) Technological advances have meant that these radioactive elements can be made in laboratory settings without the destructive pyrotechnics of the drug – 20th century. The reactor in Oak Ridge, Tennessee, is one of the very few suppliers of californium-252.
‘The reason they can create these elements is because they have a very high neutron current, so they can just emit further and further and further. [of their nucleon shells], ” said Katherine Shield, a chemist at the Lawrence Berkeley National Laboratory and co-author of the article, in a video call. The initial product of the reactor is’ just an absolute mess, a combination of all sorts of things’, Shield said, explaining that ‘it’s not just about making the element or making the isotope, but also about making it pure so that we can do chemistry. with it. ”
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Such heavy, radioactive elements as einsteinium and californium, as well as household names such as uranium and plutonium, form part of the actinide group: elements 89 to 103 in the periodic table. Only some of them, such as einsteinium and californium, are synthesized. Once a research team has completed the logistical work of safety protocols (to ensure that the radioactive elements, like any other laboratory material, are handled safely), the issues are mainly to ensure that they have enough material to work with and that the material is pure. enough to provide useful results. Extracting from the California production process, einsteinium can often be contaminated by the former.
The research team works with only 200 nanograms of einsteinium, an amount about 300 times lighter than a grain of salt. According to Korey Carter, a chemist now at the University of Iowa and lead author of the study, a microgram (1,000 nanograms) was previously considered the lower limit for a sample size.
“There were questions about, ‘Will the monster survive? “that we can prepare as well as possible,” Carter said in a video call. “Surprisingly, incredibly, it worked.”
The team was able to measure the binding distance of einsteinium-254 using X-ray absorption spectroscopy, in which you sprayed the sample with X-rays (this guideline also had to build a specialized container for the sample, one that would not does not crumble in the course of about three days under X-ray bombardment). The researchers looked at what happened to the light absorbed by the sample and found that the light emitted thereafter was bluish shift, meaning that the wavelengths were slightly shortened. This was a surprise because they expected a redshift – longer wavelengths – and this suggests that einsteinium’s electrons may couple differently than other elements nearby in the Periodic Table. Unfortunately, the team was unable to obtain X-ray diffraction data due to a California infestation in their sample, which would make the results of the method muddy.
Previously, researchers assumed that they could extrapolate certain tendencies seen in lighter elements to the heavier actinide elements, such as how they absorb light and how the size of the atoms and ions of other elements, called lanthanides, decrease as their atomic numbers rise. But the new results suggest that extrapolation may not apply.
“A lot of good work has been done over the last twenty years gradually further into the actinide series, showing that … actinide chemistry is more ongoing,” Carter said. “The rules we’ve developed for smaller things may not work so well.”
Radioanalytic work was done on einsteinium shortly after its discovery in the 1950s, but little was studied at the time. about actinides in general beyond their radioactive properties). Recent research has shown that bonding distances of einsteinium – the average length of the bond between the nuclei of two atoms in a molecule –wash a little shorter than expected. The result, according to Carter, is a ‘meaningful first data point’.
Like so many other scientists during this pandemic, the team could not do it follow-up experiments they planned. When they finally got back into the lab, most of their samples had expired. But as with every first step, this step will definitely be followed. It’s just a matter of when.