New approach to detect ultra-rare part-per-sextillion isotopes could also sharpen dark matter searches

The detection and study of isotopes, atoms of the same element that have different numbers of neutrons, could expand the scope of physics research and enable new scientific discoveries. The science-journalism coverage adds useful context, while the strongest evidential footing still comes from the underlying data, papers or institutional documentation.

It matters because cosmology operates at the edge of what current instruments can measure, where systematic errors and model assumptions are never trivial. Small discrepancies between independent measurements have historically pointed toward missing physics rather than simple calibration errors, and the ongoing tension in the Hubble constant is a live example of how a persistent disagreement between methods can reshape the theoretical landscape. Each new dataset that approaches this territory with independent systematics adds real information to a problem that has resisted easy resolution for more than a decade. This article has been reviewed according to Science X's editorial process and policies. So far, rare isotopes have been primarily detected using a technique known as accelerator mass spectrometry (AMS), which accelerates atoms, to then measure their mass and charge.

Researchers at the University of Science and Technology of China and the Chinese Academy of Sciences recently developed a new technique for detecting and counting individual atoms. Using this technique, outlined in a paper published in Nature Physics, they successfully detected the rare radioactive isotope argon-42 (⁴²Ar) in the atmosphere at an abundance of.

Scientists searching for dark matter have observed its decay signature in large liquid-argon detectors, but its isotopic abundance at the 10⁻²¹ level had always appeared far out. Meanwhile, we had been developing the ATTA method for analyzing ³⁹Ar, whose environmental abundance is at a much more reasonable level of 10⁻¹⁶.

This initial step removed the abundant isotope ⁴⁰Ar from the gas sample, while increasing the count rate of the rare ⁴²Ar isotope by approximately 450 times. Its detection limit is determined solely by the counting rate and measurement duration, a unique characteristic among trace analysis methods.

The relevance goes beyond one dataset because even small shifts in measured parameters can matter when the field is testing the limits of the standard cosmological model. The Lambda-CDM framework describes the observable universe with remarkable economy, but its success rests on two components, dark matter and dark energy, whose physical nature remains entirely unknown. Any credible measurement that tightens or loosens the constraints on those components moves the entire theoretical enterprise forward, regardless of whether the immediate result looks dramatic on its own terms.

Their calculations suggest that the rare isotope had an atmospheric abundance of (6.1 ± 0.5) × 10⁻²¹. Discover the latest in science, tech, and space with over 100, 000 subscribers who rely on Phys. org for daily insights.

Because this item comes through Phys. org Physics as science journalism, it should be treated as contextual reporting rather than primary evidence. Good science reporting can identify why a result matters, connect it to the wider literature and make technical work readable, but the decisive evidence remains in the original paper, dataset, mission release or technical record. That distinction is especially important when a story is later repeated by aggregators, because repetition increases visibility, not evidential strength.

The next step is to see whether the effect survives when independent surveys, different calibration strategies and tighter control of systematic uncertainties enter the picture. Programmes such as Euclid, DESI and the Rubin Observatory will deliver datasets over the next several years that cover the same parameter space with largely independent methods. If the current signal persists through those tests, its theoretical implications will become impossible to set aside.

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