Thorium Nuclear Clocks: A New Frontier of Precision ⚡ экспресс
This review analyzes current progress in building solid-state nuclear clocks based on the low-energy nuclear transition (a sudden jump in the nucleus's energy) of thorium-229 (8.4 eV). When embedded in a CaF crystal, the transition's lifetime reaches 641 seconds, promising exceptional stability. The main hurdle is inhomogeneous spectral broadening (frequency blurring) caused by strains and electric fields from defects and thorium atoms themselves. Remarkably, such a low-energy nuclear excitation is unique and eliminates the need for bulky accelerators.
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.