发表机构
Shanxi University; Hefei National Laboratory（山西大学; 合肥国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出无磁场校准的方法，利用磁不敏感时钟跃迁测定$^{40}$K超冷费米气体的基态超精细常数$A$，将不确定度降低近三个数量级，为相关领域提供改进参考。
AI 中文摘要
超精细常数$A$是超精细结构的关键参数，是精密光谱学和计量学的基础。本文提出一种无磁场校准的方法，利用一对磁不敏感（“时钟”）跃迁，测定$^{40}$K超冷费米气体的基态超精细常数$A$，克服了传统方法对严格磁场校准的要求。我们在一定磁场范围内以赫兹级分辨率测量这两个磁不敏感跃迁间的频率，得到基态超精细常数$A=-h\times285.730536(2)\text{MHz}$，绝对不确定度约为$2\textrm{Hz}$。该值相比此前的测定结果，不确定度降低了近三个数量级，为$^{40}$K的高精度光谱学和计量学提供了大幅改进的参考。
英文摘要
Hyperfine constant $A$ is a key parameter of the hyperfine structure and underpins precision spectroscopy and metrology. In this Letter, we develop a magnetic-field-calibration-free method for determining the ground-state hyperfine constant $A$ in an ultracold $^{40}$K Fermi gas by utilizing a pair of magnetically insensitive ("clock") transitions. This overcomes the stringent magnetic-field calibration requirements of conventional methods. We measure the transition frequency between these two magnetically insensitive transitions with Hz-level resolution over a range of magnetic fields, and obtain the ground-state hyperfine constant $A = -h\times 285.730536(2)\,\mathrm{MHz}$, corresponding to an absolute uncertainty of about $2\,\mathrm{Hz}$. Our value reduces the uncertainty by nearly three orders of magnitude compared with previous determinations, providing a substantially improved reference for high-precision spectroscopy and metrology with $^{40}$K.
Journal refPhys. Rev. Lett. 137, 133401 (2026)
