1. Energy of the $^{229}$Th Nuclear Clock Isomer Determined by Absolute $\gamma$-ray Energy Difference
- Author
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Yamaguchi, A., Muramatsu, H., Hayashi, T., Yuasa, N., Nakamura, K., Takimoto, M., Haba, H., Konashi, K., Watanabe, M., Kikunaga, H., Maehata, K., Yamasaki, N. Y., and Mitsuda, K.
- Subjects
Nuclear Experiment ,Physics - Atomic Physics - Abstract
The low-lying isomeric state of $^{229}$Th provides unique opportunities for high-resolution laser spectroscopy of the atomic nucleus. We determine the energy of this isomeric state by taking the absolute energy difference between the excitation energy required to populate the 29.2-keV state from the ground-state and the energy emitted in its decay to the isomeric excited state. A transition-edge sensor microcalorimeter was used to measure the absolute energy of the 29.2-keV $\gamma$-ray. Together with the cross-band transition energy (29.2 keV$\to$ground) and the branching ratio of the 29.2-keV state measured in a recent study, the isomer energy was determined to be 8.30$\pm$0.92 eV. Our result is in agreement with latest measurements based on different experimental techniques, which further confirms that the isomeric state of $^{229}$Th is in the laser-accessible vacuum ultraviolet range., Comment: 6 pages, 4 figures, 2 tables
- Published
- 2019
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