In a groundbreaking experimental breakthrough that has long been awaited by the nuclear physics and chemistry communities, researchers at the University of Cologne have conclusively demonstrated a rare and elusive atomic decay pathway for technetium-98 (Tc-98). Published in the esteemed journal Physical Review, this study confirms the electron capture decay mode of Tc-98, providing concrete proof of a decades-old theoretical prediction. This accomplishment not only deepens our atomic-level understanding of technetium isotopes but also enriches the broader chart of nuclides — a nuclear equivalent of the periodic table — by adding critical new decay information.
Electron capture decay, a process in which an atomic nucleus absorbs an inner-shell electron, converting a proton into a neutron, has been a detailed conceptual framework for many isotopes, yet direct empirical evidence for technetium-98’s participation in this mode remained unavailable until now. This experiment marks the first time such a decay has been identified and observed with exceptional clarity, thanks to innovative detection methods meticulously employed by the Cologne research group. The transformation triggered by electron capture effectively transmutes the parent element into a different daughter nucleus, revealing essential pieces of nuclear stability and structural puzzle parts.
Technetium, an element with no stable isotopes, plays a pivotal role in both fundamental nuclear physics and practical applications such as nuclear medicine. While technetium-99 is widely studied due to its prevalence and medical utility, technetium-98’s properties have largely eluded researchers due to its rarity and challenging experimental conditions. The presence of techno-98 in minuscule quantities — approximately 0.06 micrograms within three grams of Tc-99 samples — has rendered direct observations nearly impossible, creating a longstanding experimental barrier that the Cologne team has now successfully overcome.
The research leveraged the advantages of the Clover detector setup at the Institute of Nuclear Physics, an apparatus specialized in gamma-ray spectroscopy, to capture the characteristic gamma emissions indicative of nuclear decay processes. Over the span of 17 days, the team recorded approximately 40,000 decay events attributable to electron capture by Tc-98 nuclei. Crucial to this achievement was a specially engineered lead shielding devised to suppress the overwhelming background radiation from technetium-99, isolating the subtle electron capture signals from the otherwise dominant radioactive noise.
Detailed analysis reveals that although the primary decay pathway of Tc-98 results in the formation of ruthenium-98 (Ru-98), about 0.3 percent of the measured decays proceed via electron capture, producing molybdenum-98 (Mo-98). This minor yet definitive branch of decay was theorized previously but lacked empirical validation until this experiment. The ramifications of this finding extend beyond technetium isotopes themselves, offering insights into the behavior and transformations of nuclei near this region on the nuclear chart, and helping physicists refine nuclear models regarding proton-to-neutron conversion probabilities and energy level transitions.
PD Dr. Erik Strub, leading the Nuclear Chemistry department at the University of Cologne, emphasized the significance of this discovery. Although the quantifiable fraction of this decay route seems small, it holds substantial weight in refining nuclear decay schemes and advancing our comprehension of nuclear structure. He described it as a critical step forward in piecing together the intricate details of nuclear stability and isospin symmetries within mid-weight nuclei. The study also demonstrates the power of combining sophisticated detector technologies with rigorous background suppression to unlock rare decay phenomena.
This new evidence for technetium-98’s electron capture decay not only completes a gap in the decay map of this isotope but also enriches the overall nuclear periodic table or the chart of nuclides. Future iterations of this chart will highlight this newly confirmed decay mode with a red corner mark on the Tc-98 field, visually symbolizing this addition to our nuclear knowledge base. Such annotations serve as crucial references for experimentalists and theorists working on nuclear models, decay chains, and isotopic abundances.
The physics underlying electron capture decay involves subtle quantum mechanical and nuclear interactions between the nucleus and its surrounding electron cloud. The probability of electron capture depends intricately on factors such as nuclear energy states, electron orbital distributions, and the balance of nuclear forces. Confirming such rare decay events experimentally provides valuable parameters for nuclear matrix elements and helps calibrate theoretical models predicting decay half-lives and modes for unstable isotopes.
With this landmark experiment now conclusively demonstrating electron capture decay branching in technetium-98, the University of Cologne team intends to investigate similar rare decay processes in neighboring isotopes. This continued research promises to unveil systematic patterns and underlying principles governing nuclear transformations in this part of the nuclear landscape. Unlocking these rare decay channels will enhance our fundamental insight into nuclear synthesis, nucleosynthesis pathways in astrophysical processes, and nuclear stability far from the valley of stability.
The success at Cologne represents a subtle victory for experimental nuclear physics, characterized by ingenuity, patience, and precise technical craftsmanship. Detecting such low-yield phenomena required extensive measurement times, careful sample preparation, and an acute sensitivity to discriminate activity amid dense radioactive backgrounds. Enabling the observation of about 40,000 targeted decay events confirms not only the feasibility of studying exceedingly rare isotopic behavior but also the profound richness awaiting discovery in nuclear decay modes.
In summary, the University of Cologne’s first observation of electron capture decay of technetium-98 marks a major milestone in nuclear research, confirming theoretical frameworks from the 1990s and providing a refined understanding of nuclear decay channels. Beyond augmenting the nuclear periodic table with new, experimentally verified data, this work paves the way for exploring adjacent isotopic territories with similar low-probability, yet fundamentally informative, nuclear decay pathways. It reflects the relentless quest of nuclear physics to map the uncharted territories of atomic nuclei and the dynamics that govern their transformations.
As this new decay branch is integrated into nuclear databases, atomic physicists and chemists worldwide will recalibrate their models and applications, from radiochemistry to medical isotope synthesis. The delicate interplay of nuclear forces manifested in these subtle decay processes underlines the critical role of experimental validation for theories that shape our grasp of matter at its most fundamental level. Thus, the humble technetium-98 isotope has now stepped into the spotlight, revealing secrets that only patience, precision, and perseverance could bring to light.
Subject of Research: Electron capture decay of technetium-98
Article Title: Electron-capture decay of 98Tc
News Publication Date: 22-Oct-2025
