International Team Measures Niobium-94 Neutron Reactions, Explaining Anomalous Molybdenum-94 Abundance in the Solar System

An international team of physicists has, for the first time, conducted a comprehensive study of the interactions between neutrons and the niobium-94 isotope. The findings have been published in Physical Review Letters. The study suggests that the elevated abundance of molybdenum-94 in the primordial material of the solar system can be explained by a series of neutron-involving nuclear reaction processes inside old stars, without requiring the introduction of previously unknown special formation mechanisms.

The research was led by Alberto Mengoni, a researcher at the Italian National Institute for Nuclear Physics. The team conducted experiments using the n_TOF facility at CERN, focusing on tracking the interactions between neutrons and niobium-94 atoms. The n_TOF facility is used to study nuclear structure and the formation mechanisms of heavy elements, helping scientists measure neutron-related nuclear reaction data with greater precision.

During stellar evolution, elements heavier than iron typically form in environments such as massive dying stars or neutron star mergers. The fundamental pathway involves lighter element nuclei successively capturing neutrons and undergoing a series of nuclear reactions. Scientists have previously been able to estimate the abundance ratios of most heavy elements and their isotopes in the universe based on this process.

However, in 2003, researchers analyzing samples from the ancient Murchison meteorite found that the molybdenum-94 content in the primordial material of the solar system was significantly higher than theoretical calculations predicted. This "molybdenum anomaly" has long sparked discussion, with the key question being whether it implies the existence of unknown physical processes inside stars.

This experiment provided more precise data on the neutron capture behavior of niobium-94. Niobium-94 decays to form molybdenum-94, but it can also capture a neutron and transform into niobium-95. Previously, the scientific community had limited knowledge of how frequently this competing process occurs, making it difficult to accurately assess the production of molybdenum-94 in old stars.

The experimental results show that molybdenum-94 can indeed be formed through the decay of niobium-94, and the frequency of this process is higher than previously predicted by existing theories. Based on these findings, the research team concludes that the discrepancy between measured and theoretical values of molybdenum-94 in the primordial material of the solar system can be explained by the new nuclear reaction data, without the need to hypothesize additional unknown physical mechanisms participating in the chemical evolution of stellar interiors.