Controlling ²²⁹Th isomeric state population in a VUV transparent crystal

Area of Science:

• Nuclear physics
• Atomic physics
• Quantum optics

Background:

• The thorium-229 (²²⁹Th) isotope possesses a unique low-energy, long-lived nuclear isomeric state.
• This state is a promising candidate for ultra-precise nuclear clocks, but requires controlled excitation and de-population.

Purpose of the Study:

• To investigate controlled population and de-population methods for the ²²⁹Th isomeric state.
• To assess the feasibility of ²²⁹Th for nuclear clock applications.

Main Methods:

• Population of the ²²⁹Th isomer via resonant X-ray pumping in a ²²⁹Th-doped CaF₂ crystal.
• Detection of radiative decay and measurement of the isomeric half-life.
• Observation and characterization of an "X-ray quenching" effect for de-population.

Main Results:

• Successful population of the ²²⁹Th isomeric state using X-ray pumping.
• Measured decay half-life of 447(25) s with a transition wavelength of 148.18(42) nm.
• Demonstrated "X-ray quenching" for on-demand de-population, reducing the effective half-life.

Conclusions:

• Resonant X-ray pumping provides a viable method for exciting the ²²⁹Th isomer.
• "X-ray quenching" offers a novel technique for controlling the ²²⁹Th isomer's state.
• These findings advance the development of ultra-precise nuclear clocks based on ²²⁹Th.