Laser-based conversion electron Mössbauer spectroscopy of ²²⁹ThO₂.

Area of Science:

• Nuclear Physics and Spectroscopy
• Condensed Matter Physics
• Metrology

Background:

• The Thorium-229 (²²⁹Th) nuclear isomeric state offers potential for nuclear clocks and fundamental physics tests.
• Current methods for studying the ²²⁹Th isomer in solids require high-bandgap materials, limiting applications.
• Laser Mössbauer spectroscopy offers high sensitivity for probing nuclear environments and developing sensors.

Purpose of the Study:

• To demonstrate a new technique for probing the ²²⁹Th nuclear isomeric state in a solid host.
• To overcome the limitations of vacuum ultraviolet (VUV) transmissive host materials in previous studies.
• To explore the potential for developing a conversion-electron-based nuclear clock.

Main Methods:

• Demonstration of laser-induced conversion electron Mössbauer spectroscopy (CEMS) on a thin Thorium dioxide (ThO₂) sample.
• Utilized a ThO₂ sample with a bandgap (approx. 6 eV) significantly smaller than the ²²⁹Th isomeric transition energy (8.4 eV).
• This method is an alternative to fluorescence spectroscopy, which is incompatible with lower-bandgap materials.

Main Results:

• Successfully performed CEMS on the ²²⁹Th isomer within ThO₂.
• The technique is compatible with materials having bandgaps smaller than the nuclear transition energy.
• This expands the range of host materials suitable for studying the ²²⁹Th isomer.

Conclusions:

• Laser-induced CEMS provides a viable method for studying the ²²⁹Th isomer in lower-bandgap materials.
• This opens new avenues for developing highly sensitive solid-state nuclear clocks and sensors.
• The findings pave the way for a new generation of ²²⁹Th-based metrology and fundamental physics research.