Excitation of Thorium-229 doped in crystals using a pulsed laser toward nuclear clocks

Résumé fourni par la source

229Th has the uniquely low nuclear first excited state (229 mTh) with the excitation energy of 8.356 eV. This allows excitation using vacuum ultraviolet (VUV) lasers, which opens up the possibility of realizing a clock based on nuclear energy levels, called nuclear clocks. Unlike atomic clocks, nuclear clocks can be used as clocks even when embedded in solids. In 2024, the world’s first laser excitation of 229Th was finally achieved using 229Th-doped CaF2. In solid crystals, interactions between the nuclear electric quadrupole moment and local electric field gradients split nuclear energy levels. When using crystalline targets, it is not easy to observe weak transitions of quadrupole splitting due to background radioluminescence of 229Th and its daughter nuclei. We performed spectroscopy experiments of 229Th-doped CaF2 crystals by combining a vacuum ultraviolet laser with a linewidth of about 30 MHz and a detector that can significantly reduce radioluminescence. In these proceedings, we report a weak transition which is not measured from the other groups.

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