Thorium Nuclear Clocks: A New Frontier of Precision ⚡ экспресс
We review the technology and limits of the current generation of atomic clocks, then analyze the prospects of solid-state nuclear clocks based on the anomalously low-energy nuclear transition of Th-229 (8.4 eV). In CaF crystals, this transition exhibits an exceptionally long lifetime of 641 s. The key challenge is inhomogeneous spectral line broadening from internal strains and electric field gradients generated by both thorium atoms and intrinsic crystal defects. Understanding and mitigating these effects demands a multidisciplinary approach at the intersection of nuclear physics, atomic and molecular optics (AMO), and solid-state physics. Solving these problems paves the way for clocks that could surpass existing ones in compactness and stability.
Ordinary atomic clocks rely on spectroscopy — counting electron oscillations. Thorium-229 nuclear clocks address the nucleus itself. Its excited state lives for 641 seconds: for nuclear physics, this is a pendulum in thick syrup, where one swing lasts an eternity, but is impeccably stable.
Placing such nuclei in a crystal, physicists face a problem: lattice defects act like an uneven floor, disrupting the rhythm of each pendulum in its own way. The task is to level this floor. Then the clocks will become more accurate: an error of one second over the entire age of the Universe. They will notice the difference in the passage of time between floors and test the Standard Model of physics for strength.
🎯 Thorium-229 is the only nucleus whose transition can be triggered by a regular ultraviolet laser, rather than hazardous gamma radiation. This makes the experiments tabletop and safe.