Counting electrons reveals thorium’s nuclear tick in solid clock, Pg11

Key Highlights:

• Researchers have successfully detected the excitation of Thorium-229 nuclei in a solid clock using a laser-based method.
• The experiment involved using Thorium dioxide and counting electrons emitted during the decay of excited nuclei.
• A clear resonance was detected at 2,020,407.5 GHz, consistent with previous studies on Thorium-229.
• The inferred internal conversion lifetime of 12.3 seconds suggests the clock would only be off by one second every 15.8 billion years.

Detailed Insights:

• The core principle involves using the nucleus of Thorium-229 as a timekeeping mechanism, which is less sensitive to external disturbances compared to atomic clocks.
• The process relies on exciting Thorium-229 nuclei with vacuum-ultraviolet (VUV) laser pulses and detecting the electrons emitted during internal conversion.
• Researchers suppressed ordinary photoelectrons using timed electric fields to isolate and count the delayed electrons associated with nuclear decay.
• This advancement allows for the development of stable, high-precision nuclear clocks and sensors capable of probing the nuclear environment of different materials.
• The design facilitates substantial miniaturization, as the nuclear clock can be monitored by measuring the current of emitted electrons.

Scientific/Technical Concepts Involved:

• Thorium-229: An isotope of thorium with a unique nuclear excited state suitable for nuclear clocks.
• Internal Conversion: A decay process where a nucleus transfers energy to an electron instead of emitting a photon.
• Vacuum-Ultraviolet (VUV): A region of the electromagnetic spectrum with wavelengths shorter than ultraviolet light, used to excite thorium nuclei.