NEW DELHI: For the first time, scientists have unveiled crucial properties of the mysterious, radioactive substance promethium, nearly eight decades after the elusive rare earth element was discovered. Promethium, one of the 15 lanthanide elements at the bottom of the periodic table, exhibits strong magnetism and unusual optical characteristics, making it important for modern electronic devices.”They are used in lasers; they are part of the screens of your smartphone. They are also used in very strong magnets in wind turbines and electric vehicles,” said Ilja Popovs, a research and development staff member at Oak Ridge National Laboratory (ORNL) and co-author of a new study published in the journal Nature.As per a Live Science report, Promethium itself, discovered by ORNL scientists in 1945, has a few minor applications in atomic batteries and cancer diagnostics. However, scientists have had a limited understanding of the element’s chemistry, hindering more widespread uses. Studying the radioactive element has posed a decades-long challenge due to the difficulty of securing a suitable sample. “Promethium doesn’t have a stable isotope — they’re all radioactive, meaning that they are decaying with time,” said team member Alexander Ivanov. “You get this element through a fission process, so it’s scarce and difficult to study.”ORNL is the US’ only producer of promethium-147, an isotope of the element with a radioactive half-life of 2.6 years. Using a method developed last year, the researchers separated this isotope from nuclear reactor waste streams, creating the purest possible sample for study. The team combined this sample with a ligand, a molecule designed to trap metal atoms, to form a stable complex in water. The coordinating molecule, known as PyDGA, formed nine promethium-oxygen bonds, allowing researchers to analyze the bonding properties of a promethium complex for the first time.However, the analysis was challenging. “Because promethium is radioactive, once it’s decaying, it’s getting transmuted into the adjacent element, which is samarium,” Ivanov said. The team used an extremely specialized technique called synchrotron-based X-ray absorption spectroscopy. High-energy photons generated by a particle accelerator bombarded the promethium complex, building a picture of the positions of atoms and the lengths of bonds. This allowed the team to focus on the key promethium-oxygen bond, discounting any contaminating samarium.”Promethium was the last puzzle piece among those elements,” Popovs said. The ligand provided a way to have a stable complex for all of the lanthanides, enabling the team to study the fundamental physical chemical properties of these complexes across the whole series. Understanding periodic trends helps scientists develop new and more efficient methods to separate these valuable metals. The ORNL team is now studying promethium in water to build a clearer picture of its coordination environment and chemical behavior. “Hopefully, the fundamental insights that we’re providing will inform other scientists how to design better separation technologies and can perhaps spur more interest in studying it for other applications,” Popovs said.
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