Chemistry riddle: Lasers probe nuclear structure of elements to test periodic table’s limit
An international team of scientists has shed light on the extreme ends of neutron and proton numbers.
Their goal is to investigate the limits of the periodic table of chemical elements. How far can the periodic table go and will we ever synthesize the last element?
In a new study , published in the journal Nature, the team provided insight into the structures of the atomic nuclei of fermium (element 100) and nobelium (element 102). They did so with different numbers of neutrons.
These are two chemical elements that are very difficult to synthesize and are at the heavier end of the periodic table of elements.
Using lasers beams to measure the nuclear radius of isotopes at the end of periodic table
Elements at the end of the periodic table are produced artificially via accelerator-driven nuclear reactions or reactor-breeding mechanisms. The fact that they do not occur naturally poses a challenge for scientists, as they are often difficult to produce and have increasingly short half lives.
The international team behind the new study set out to probe some of these elements to better understand them. They used laser spectroscopy to measure the nuclear radius of several isotopes of nobelium and fermium.
During their research, they used laser equipment to probe nobelium atoms and measure their atomic hyperfine structure. They produced a key isotope from the decay of lawrencium atoms. These atoms were captured from a beam of nuclear reaction products and pulse-heated off a catcher filament. The researchers then resonantly ionized the atoms and identified them via their alpha decay fingerprint.
In their study, they found that the trend across a key neutron number was smooth. This is unlike the lighter elements of the nuclear chart, where upward kinks cross shell closures. This observation indicates that nuclear shell effects have a reduced influence when it comes to the so-called superheavy elements.
What happens at the extremes of neutron and proton numbers?
The new research builds on a 2016 study, in which Professor Cheal was also involved. That study, published in the journal Nature, reported the first instance of laser spectroscopy being performed on nobelium.
Nobelium is a synthetic chemical element with the atomic number of 102. The element was first synthesized by a team of scientists working at the Nobel Institute of Physics in Stockholm in 1957. To date, it has only been produced in very small quantities, and its only use is for scientific research.
By studying elements like nobelium, scientists can determine how far we can stretch the periodic table. This could have incredibly important implications for materials science and other fields.
"A perennial question in nuclear physics is to ask what happens at the extremes of neutron and proton numbers and where the periodic table may end ," Professor Bradley Cheal, one of the researchers from the University of Liverpool's Department of Physics, explained in a press statement . "This study provides new answers to this."
"Here at Liverpool, we played an important role in the nobelium experiments that form part of this study," he continued. "This work combined our expertise in laser spectroscopy, a method traditionally limited to radioactive isotopes of naturally occurring elements, with a track record at specialist facilities capable of producing the heaviest elements."
