Welcome

• 学庆 颜 (PKU)
• 学庆 颜 (P)

Collective and microscopic approaches to $^{229m}\mathrm{Th}$

• 晓涛 贺 (NUAA)

Direct laser excitation of the Th-229 nucleus and recent progress on nuclear clock

• Ke (科) Zhang (张) (北京理工大学（Beijing Institute of Technology）)

We report the first direct laser excitation of the Th-229 nuclear transition in Th-doped CaF2 crystals using a tabletop tunable laser system. The Th: CaF2 crystals are grown at TU Wien with up to 5×1018 cm-3 Th-229 concentration, and a VUV laser system developed at PTB, that provides a spectral photon flux of more than 2×104 photons/(s Hz). A resonance fluorescence signal is observed in two crystals with different Th-229 dopant concentrations, while it is absent in a control experiment using Th-232. The nuclear resonance for the Th4+ ions in Th: CaF2 is measured at the wavelength 148.3821(5) nm, frequency 2020.409(7) THz, and the fluorescence lifetime in the crystal is 630(15) s. Because of the higher density of photon states in the dielectric optical medium, the measured spontaneous M1 decay rate is expected to be enhanced relative to the rate in vacuum by a factor n3 where n is the refractive index. Applying this correction, the measured radiative lifetime of 630(15) s corresponds to an isomer half-life in vacuum of 1740(50) s. These results pave the way towards a high-resolution Th-229 nuclear laser spectroscopy and realizing optical nuclear clocks. Dr. Ke Zhang graduated with a bachelor’s degree in physics from Shanxi University in July 2014, where she earned second prize of Science and Technology Challenge Cup of Shanxi university in 2013. She then pursued a PhD at the China Academy of Engineering Physics, earning multiple scholarships. From 2020 to 2022, she worked at GSI Helmholtz institute in Germany, where she solved two challenging problems in atomic and molecular spectroscopy: the first detection of the two lowest-lying atomic states in actinium [1] and the detection of fast oscillations of nuclear mass using molecular spectroscopy [2]. In 2022, she joined Ekkehard Peik’s group for her second postdoctoral research position in PTB, where she was assigned the challenging scientific task of laser-exciting the Th-229 nucleus—a long-standing puzzle in Th-229 research since 1976. Together with her colleagues and collaborators, she succeeded in exciting the Th-229 nucleus on April 29, 2024 [3]. [1] Phys. Rev. Lett. 125, 073001 (2020). [2] Phys. Rev. Lett. 129, 031302 (2022). [3] Phys. Rev. Lett. 132, 182501 (2024).

三价钍-229离子中的原子核超精细混合效应

• 旭 王 (中国工程物理研究院研究生院)

囚禁$^{229}\mathrm{Th}^{3+}$离子中同核异能态的单、双光子激发理论研究

• Wu Wang (ITP, Beijing)

原位光核反应产生229Th核钟晶体的实验研究

• 笛 吴 (China Institute of Atomic Energy)

国内外高灵敏光子探测器相关研究进展

• Ping Chen (Xi'an Institute of Optics and Precision Mechanics of CAS)

NH₄B₄O₆F（ABF）氟氧硼酸盐晶体在二次谐波产生中实现高效真空紫外光生成的系统研究 [remote]

• Fangfang Zhang (新疆理化所)

面向钍核激发的VUV光梳

• 林强 华 (武汉精测院)

$^{229}\mathrm{Th}$原子核的NEIES与NEEC研究 [remote]

• 杨洋 徐 (国防科大)

以缪子催化聚变为例简要介绍J-PARC低能缪子谱学实验 [remote]

• Ce Zhang (University of Liverpool)

HIAF的缪子源及Th研究

• 良文 陈 (中国科学院近物所)

Some progress on Muonic Th-229 spectroscopy [remote]

• Leyun Gao (Peking University)