Probing light dark matter with a portable nuclear clock: the throrium-229 atoms transition frequency and the tell-tale glow

This energy shift requiresa slightly higher, ultraviolet frequency, resulting in a faster tick rate that could match or surpass the accuracy of the atomic clock. But the nuclear clock’s biggest potential advantage is the combination of precision and stability. Particles in the nucleus are less sensitive than electrons to disturbances such as electromagnetic fields — meaning that a nuclear clock could be portable and robust. “It becomes insensitive in a way that is kind of unthinkable in terms of how our clocks work today,” says Anne Curtis, an experimental physicist at the National Physical Laboratory in Teddington, UK.

Nuclear Clocks are 100 million times more sensitive to the effects of dark matter than atomic ones, if changes in forces can be amplified in the nuclear transition frequency. The latest result — which pinpoints the frequency with an accuracy of 13 decimal places — is already precise enough to narrow down the possible energy ranges in which light dark matter could exist, says Fuchs. Nuclear physics could also benefit from the more precise transition frequency, which could help scientists to distinguish betweendifferent possible shapes of the throrium-229 nucleus, she adds.

The breakthrough was achieved by probing thorium-229 nuclei with a laser device. The set-up is not technically a clock, because it has not been used to measure time. But such impressive results make the development of a nuclear clock seem possible, says Safronova.

The comb’s settings — including the width of the gaps between the lines, or ‘teeth’ — were calibrated using the atomic clock and could be tweaked. The team conducted several experimental runs, and when they observed the tell-tale glow produced when thorium-229 atoms decay from their excited state, they used the settings to calculate the frequency driving the signal.

For the first time, observing the transition felt amazing, says study co-author Chuankun Zhang. “We spent the entire night doing all the tests to check if this is actually really the signal that we were looking for,” he says.

Finding the right kind of atomic nucleus to use, and determining the frequencies needed to induce its shift to a different energy state, have been a fifty-year process for physicists. In the 1970s, indirect evidence suggested that thorium-229 had a bizarrely low-energy nuclear transition2 — one that might eventually be triggered by tabletop lasers. Scientists found the required frequencies last year, and they were able to initiate shift with a laser this year.

The laser system also needs honing. This technique has high potential, according to a physicist at Texas A&M University. She says that the source is going to be used in the future clock.

The Nature Podcast: How floods and heatwaves affected the sense of smell in the bumblebee’s sense of savour

How unprecedented floods in Brazil have helped and hindered paleontologists, and the ‘AI scientist’ that does everything from literature review through to manuscript writing, to an extent.

Don’t miss an episode. Subscribe to the Nature Podcast on

  Apple Podcasts



,



  Spotify



,



  YouTube Music



 or your favourite podcast app. There is also an RSS feed for the NaturePodcast.

One day, researchers hope to translate this approach into a human therapy, by using T cells to fine- tune the inflammation response. Immune cells rush to the scene following injury to the central nervous system,causing a complex array of effects, both good and bad. In this work researchers have identified the specific kind of T cells that amass at the site, and used them to create an immunotherapy that helps the mice recover more quickly from injuries by slowing damage to neurons.

The star that got partially shredded by a supermassive black hole, not just once, but twice, and how heatwaves could mangle bumblebees’ sense of smell.