Nuclear clock method to detect dark matter using thorium-229

Scientists have been on the hunt for dark matter for nearly a century now. This elusive substance is thought to account for about 80% of the universe's mass, playing a crucial role in our understanding of various physical phenomena. Despite countless efforts to detect dark matter ranging from experiments in particle accelerators to searches for cosmic radiation our grasp of its fundamental properties remains quite limited.

Researchers believe that creating a nuclear clock could shed light on the effects of dark matter. This innovative clock would utilize the atomic nucleus to measure time with remarkable precision. Just last year, physicists in Germany and Colorado made strides toward developing such a clock using thorium-229.

When scientists at the Weizmann Institute caught wind of this breakthrough, they recognized an opportunity to boost the search for dark matter, even before the nuclear clock is fully realized. Teaming up with the German researchers, they published a study suggesting a novel approach to detect dark matter's impact on the properties of thorium-229.

An atomic nucleus has a specific resonance frequency, much like how a child on a swing needs the right timing to swing smoothly. By exciting the nucleus with radiation at this frequency, it can shift between two quantum states. While most materials require strong radiation for this process, thorium-229 stands out. Its low resonance frequency can be manipulated using standard laser technology, making it a promising candidate for a nuclear clock.

For many years, progress in measuring thorium-229's resonance frequency was painstakingly slow. To pinpoint this frequency, physicists shine a laser on the nucleus at various frequencies and watch for energy absorption or emission. They then compile an absorption spectrum to identify the resonance frequency.

After nearly five decades of hurdles, last year brought significant breakthroughs. A team in Germany reported relatively accurate measurements, while a group in Colorado delivered results that were impressively precise.

Reference

by Weizmann Institute of Science The dark side of time: Scientists develop nuclear clock method to detect dark matter using thorium-229

Phys.org Available at- https://phys.org/news/-dark-side-scientists-nuclear-clock.html

(Assessed: 17th July 2025)