@article{35e485e82f06430789d73c79ce5f7923,
title = "Energy of the Th 229 Nuclear Clock Isomer Determined by Absolute γ -ray Energy Difference",
abstract = "The low-lying isomeric state of Th229 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 γ ray. Together with the cross-band transition energy (29.2 keV→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±0.92 eV. Our result is in agreement with the latest measurements based on different experimental techniques, which further confirms that the isomeric state of Th229 is in the laser-accessible vacuum ultraviolet range.",
author = "A. Yamaguchi and H. Muramatsu and T. Hayashi and N. Yuasa and K. Nakamura and M. Takimoto and H. Haba and K. Konashi and M. Watanabe and H. Kikunaga and K. Maehata and Yamasaki, {N. Y.} and K. Mitsuda",
note = "Funding Information: We thank D. Aoki for support to conduct this research and T. Yamamura for technical support to prepare the U233 source. We also thank T. Masuda, A. Yoshimi, K. Yoshimura, and A. Hinton for their valuable comments on the manuscript. This work was supported by JSPS Grant-in-Aid for Scientific Research (B) Grant No. JP18H01241. A. Y. acknowledges Technology Pioneering Projects in RIKEN. The U233 sample used in this study is provided by the U233 cooperation project between JAEA and the Inter-University Cooperative Research Program of the Institute for Materials Research, Tohoku University (Proposal No. 17K0204). H. M. is partially supported by JSPS Grant-in-Aid for JSPS Fellows Grant No. 17J07990. We fabricated the TES microcalorimeter partly using the nano-electronics fabrication facility of JAXA. The SQUID array amplifier was fabricated by CRAVITY of AIST. Publisher Copyright: {\textcopyright} 2019 American Physical Society.",
year = "2019",
month = nov,
day = "26",
doi = "10.1103/PhysRevLett.123.222501",
language = "English",
volume = "123",
journal = "Physical review letters",
issn = "0031-9007",
publisher = "American Physical Society",
number = "22",
}