Hiraki Takahiro, Okai Koichi, Bartokos Michael, Beeks Kjeld, Fujimoto Hiroyuki, Fukunaga Yuta, Haba Hiromitsu, Kasamatsu Yoshitaka, Kitao Shinji, Leitner Adrian, Masuda Takahiko, Guan Ming, Nagasawa Nobumoto, Ogake Ryoichiro, Pimon Martin, Pressler Martin, Sasao Noboru, Schaden Fabian, Schumm Thorsten, Seto Makoto, Shigekawa Yudai, Shimizu Kotaro, Sikorsky Tomas, Tamasaku Kenji, Takatori Sayuri, Watanabe Tsukasa, Yamaguchi Atsushi, Yoda Yoshitaka, Yoshimi Akihiro, Yoshimura Koji
Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530, Japan.
Institute for Atomic and Subatomic Physics, TU Wien, Vienna, 1020, Austria.
Nat Commun. 2024 Jul 16;15(1):5536. doi: 10.1038/s41467-024-49631-0.
The radioisotope thorium-229 (Th) is renowned for its extraordinarily low-energy, long-lived nuclear first-excited state. This isomeric state can be excited by vacuum ultraviolet (VUV) lasers and Th has been proposed as a reference transition for ultra-precise nuclear clocks. To assess the feasibility and performance of the nuclear clock concept, time-controlled excitation and depopulation of the Th isomer are imperative. Here we report the population of the Th isomeric state through resonant X-ray pumping and detection of the radiative decay in a VUV transparent Th-doped CaF crystal. The decay half-life is measured to 447(25) s, with a transition wavelength of 148.18(42) nm and a radiative decay fraction consistent with unity. Furthermore, we report a new "X-ray quenching" effect which allows to de-populate the isomer on demand and effectively reduce the half-life. Such controlled quenching can be used to significantly speed up the interrogation cycle in future nuclear clock schemes.
放射性同位素钍 - 229（Th）以其极低能量、长寿命的核第一激发态而闻名。这种同质异能态可被真空紫外（VUV）激光激发，并且Th已被提议作为超精密核时钟的参考跃迁。为了评估核时钟概念的可行性和性能，对Th异构体进行时间控制的激发和去激发至关重要。在此，我们报告了通过共振X射线泵浦在掺Th的VUV透明CaF晶体中实现Th同质异能态的布居，并检测其辐射衰变。测得衰变半衰期为447(25) 秒，跃迁波长为148.18(42) 纳米，辐射衰变分数与1一致。此外，我们报告了一种新的“X射线猝灭”效应，该效应可按需使异构体去布居并有效缩短半衰期。这种可控猝灭可用于显著加快未来核时钟方案中的询问周期。
