Nuclear chemists and nuclear physicists at the University of Cologne provide experimental proof of a long-suspected atomic decay pathway. The article published in 'Physical Review' shows that technetium-98 occasionally decays into molybdenum-98
For the first time, a research team from the University of Cologne has observed the electron capture decay of technetium-98, an isotope of the chemical element technetium (Tc). Electron capture decay is a process in which an atomic nucleus "captures" an electron from its inner shell. The electron merges with a proton in the nucleus to form a neutron, turning the element into a different one. The working group from the Nuclear Chemistry department has thus confirmed a decades-old theoretical assumption. The findings contribute to a more comprehensive understanding of technetium decay processes and extend the chart of nuclides – the "nuclear periodic table". The study was published under the title 'Electron-capture decay of 98Tc' in the journal Physical Review.
As early as the 1990s, researchers suspected that technetium-98 could also decay by capturing an electron, but no proof could be found, as the isotope only is available in extremely small quantities. For the current study, the Cologne research team used around three grams of technetium-99, which contains tiny traces of the rare isotope technetium-98 (around 0.06 micrograms). At the Clover measuring station of the Institute of Nuclear Physics, which detects characteristic gamma rays, approximately 40,000 electron capture decays were recorded within 17 days. This success was achieved thanks to specially designed lead shielding that almost completely suppresses the intense radiation background of technetium-99. As a result, the researchers were able to clearly detect the extremely rare signal of technetium-98 for the first time.
The measurements showed that technetium-98 predominantly decays into the isotope ruthenium-98, but in around 0.3 per cent of cases it also transforms into molybdenum-98 via electron capture. "For us, this represents a small yet significant contribution to the broader understanding of nuclear physics," says group leader PD Dr Erik Strub from the University of Cologne's Department of Chemistry. "Such precise evidence helps us better understand the stability and structure of atomic nuclei and to gradually complete the chart of nuclides piece by piece."
The study expands the fundamental understanding of nuclear decay processes. In future work, the team aims to study similar rare decay processes in neighbouring nuclides to reveal systematic patterns in the chart of nuclides. In the next edition of this map, a new red corner will be added to the technetium-98 field to symbolize the newly confirmed decay pathway.
