Research teams in Austria and China develop first nuclear clocks
The devices used thorium-229 nuclei as a timekeeping reference, achieving precision of approximately 10⁻¹⁵ during testing.
Two teams involving TU Wien in Austria and Tsinghua University and other Chinese institutions have developed what they describe as the first nuclear clocks. Nature published their results in separate papers, with the experiments demonstrating that transitions inside an atomic nucleus can provide a reference for measuring time.
The approach differs from that of the most precise existing atomic clocks, which track electrons changing energy levels. Nuclear clocks instead monitor transitions involving the nucleus, where protons and neutrons are found. Neither fusion nor fission is used in atomic timekeeping.
For the experiments, ultraviolet laser light at 148.4 nanometres was directed towards small crystals of calcium fluoride containing thorium-229. This is the only known nucleus whose energy state can be changed with ultraviolet laser light. The laser maintained its lock on the nuclear transition, producing timekeeping precision of approximately 10⁻¹⁵ — one part in a quadrillion — over the testing period.
The researchers say the technology could improve accuracy in telecommunications and satellite navigation. They also suggest potential applications in fundamental physics, but do not identify specific uses.
