Isotope Abundance Measurement by Molecular Coulomb Explosion: Proof of Concept and Initial Performance Evaluation for Carbon and Oxygen Isotope Abundance

Stable and long-lived radioactive isotopes are ubiquitous in nature and serve as unique tracers across diverse fields such as nuclear astrophysics, atmosphere chemistry, hydrology, environmental chemistry, and the diagnosis of diseases in the human body. Over the past decades, accelerator mass spectrometry and spectroscopic methods have been used to measure the abundance of stable and long-lived radioactive isotopes. However, their accuracy has been constrained by the systematic uncertainties inherent in sophisticated instrumentation and limitations in the abundance sensitivity. Here, we present a novel approach based on the fundamental mechanism of molecular Coulomb explosion fragmentation (i.e., molecules breakup as a result of Coulomb repulsion between the positively charged nuclei within molecules that are rapidly stripped of their electrons), utilizing a two-dimensional coincidence time-of-flight spectrometer to detect fragmented isotopic ion pairs. The present method enables direct determination of the isotopic abundances of ¹³C and ¹⁸O with an accuracy better than 0.02%, significantly improving abundance sensitivity by powerful identification and eliminating systematic uncertainties. Our molecular Coulomb explosion spectrometry provides high-accuracy measurement of stable and long-lived radioactive isotope abundance, with significant potential to advance isotope tracer studies in the Earth environment, anthropology, archeology, global ecological cycles, fundamental nuclear physics, and biomedicine.