X-ray-induced quenching of the $^{229}$Th clock isomer in CaF$_2$

Ming Guan; Michael Bartokos; Kjeld Beeks; Hiroyuki Fujimoto; Yuta Fukunaga; Hiromitsu Haba; Takahiro Hiraki; Yoshitaka Kasamatsu; Shinji Kitao; Adrian Leitner; Takahiko Masuda; Nobumoto Nagasawa; Koichi Okai; Ryoichiro Ogake; Martin Pimon; Martin Pressler; Noboru Sasao; Fabian Schaden; Thorsten Schumm; Makoto Seto; Yudai Shigekawa; Kotaro Shimizu; Tomas Sikorsky; Kenji Tamasaku; Sayuri Takatori; Tsukasa Watanabe; Atsushi Yamaguchi; Yoshitaka Yoda; Akihiro Yoshimi; Koji Yoshimura

arXiv · 2505.03852

X-ray-induced quenching of the $^{229}$Th clock isomer in CaF$_2$

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Abstract

Thorium-229 has the lowest nuclear-excited state (an isomer state) at approximately 8.356 eV, making it excitable with tabletop vacuum-ultraviolet lasers. Despite the recent success of laser excitation, the isomer quenching inside the solid-state environment remains unresolved. In this letter, we present experiments investigating X-ray-induced isomer quenching in the CaF$_2$ host, focusing on the effects of X-ray flux and temperature on the lifetime and yield of the isomer state. Our studies reveal a correlation between isomer production, isomer lifetime during irradiation, and post-irradiation afterglow of the target crystal across different temperatures, highlighting a strong relationship between isomer quenching and color-center dynamics. We developed a model to interpret the isomer quenching and the crystal's luminescence.

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Ming Guan, Michael Bartokos, Kjeld Beeks, Hiroyuki Fujimoto, Yuta Fukunaga, Hiromitsu Haba, Takahiro Hiraki, Yoshitaka Kasamatsu, Shinji Kitao, Adrian Leitner, Takahiko Masuda, Nobumoto Nagasawa, Koichi Okai, Ryoichiro Ogake, Martin Pimon, Martin Pressler, Noboru Sasao, Fabian Schaden, Thorsten Schumm, Makoto Seto, Yudai Shigekawa, Kotaro Shimizu, Tomas Sikorsky, Kenji Tamasaku, Sayuri Takatori, Tsukasa Watanabe, Atsushi Yamaguchi, Yoshitaka Yoda, Akihiro Yoshimi, Koji Yoshimura. 2025-05-06. X-ray-induced quenching of the $^{229}$Th clock isomer in CaF$_2$. https://arxiv.org/abs/2505.03852

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