First conceived in the burning of a hydrogen bomb on Elugelab Island in the South Pacific in 1952, the heavy element einsteinium is one of the brightest members of the Periodic Table; it does not occur naturally and is so unstable that it is difficult to get enough things, long enough, to actually study them.
Now, a team of chemists from Lawrence Berkeley National Laboratory, Los Alamos National Laboratory and Georgetown University have managed to do just that. They inspected a microscopic amount of einsteinium-254 to better understand the properties and fundamental chemical behavior of the evasive element. Their research is published today in the journal Nature.
Einstein is manufactured at Oak Ridge National Laboratory High flow isotope reactor as a by-product of the biannual production of californium-252 (another heavy element, synthesized in the laboratory, but which has commercial utility.) Technological advances have meant that these radioactive elements can be made in laboratory conditions without the destructive pyrotechnics of the medium – 20th Century Reactor in Oak Ridge, Tennessee, is one of the few suppliers of California-252.
“The reason I can create these elements is that they have a very high neutron flux, so they can simply push farther and farther and farther. [of their nucleon shells], ” said Katherine Shield, a chemist at Lawrence Berkeley National Laboratory and co-author of the paper, in a video call. The original product of the reactor is “just absolute mess, a combination of all sorts of things,” Shield said, explaining that “it’s not just about creating the element or making the isotope, it’s also about purifying it so that we can do chemistry with it. “
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Such heavy, radioactive elements, such as einsteinium and californium, as well as household names such as uranium and plutonium, are part of the actinide group: elements 89-103 in the periodic table. Only some of them, such as einsteinium and californium, are synthesized. Once a research team goes through the logistical work of safety protocols (to ensure that radioactive elements, like any other laboratory material, are handled safely), the problems first ensure that they have enough material to work with and that the material is purely sufficient to provide useful results. Extracted from the California production process, einsteinium can often be contaminated by the former.
The research team worked with just 200 nanograms of einsteinium, 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 thought to be the lower limit for a sample size.
“There were questions: ‘Will the sample survive? “We could prepare as best we could,” Carter said in a video call. “Amazing, amazing, it worked.”
The team was able to measure the binding distance of einsteinium-254 using X-ray absorption spectroscopy, in which you bombard the X-ray sample (this line of investigation also required the construction of a specialized sample holder, one that did not would shatter under X-ray bombardment within about three days). The researchers analyzed what happened to the light that was absorbed by the sample and found that the light that was subsequently emitted was changed to blue, which means that the wavelengths were slightly shortened. This was a surprise, as they had expected a change to red – longer wavelengths – and this suggests that the electrons of the einsteine may couple differently from other elements in its vicinity on the periodic table. Unfortunately, the team was unable to obtain X-ray diffraction data due to California contamination in their sample, which would renew their method results.
Previously, researchers assumed that they could extrapolate certain trends observed in lighter elements to heavier actinide elements, such as how they absorb light and how the size of atoms and ions of other elements, called lanthanides, it was decreasing as their atomic number increases. But the new results suggest that the extrapolation may not be true.
“There’s been a lot of extraordinary work over the last 20 years to progressively move the actinide series forward, showing that … actinide chemistry is happening more,” Carter said. “The rules I’ve developed for smaller things may not work as well.”
The radioanalytical work was done on einsteinium shortly after its discovery in the 1950s, but at that time, little was studied. about actinides in general beyond their radioactive properties). Recent research has shown that the distances of the einsteine bond – the average length of the connection between the nuclei of two atoms in a molecule –They were slightly shorter than expected. The result, Carter said, is a “first significant data point.”
Like many other scientists during this pandemic, the team failed to lead the follow-up experiments they had planned. When they finally returned to the lab, most of their sample degraded. But, as with any first step, it is sure to be followed by steps. It’s only a matter of time.