Probing multiple electric-dipole-forbidden optical transitions in highly charged nickel ions
Probing multiple electric-dipole-forbidden optical transitions in highly charged nickel ions
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DOI：
10.1103/physreva.103.022804
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发表时间：
2021-01
影响因子：
2.9
通讯作者：
Shiyong Liang;Tingxian Zhang;H. Guan;Qi Lu;J. Xiao;Shao-long Chen;Yao Huang;Yong-Hui Zhang;Cheng-bin Li;Y. Zou;Jiguang Li;Zong-Chao Yan;A. Derevianko;M. Zhan;T. Shi;K. Gao
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文献类型：
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作者：
Shiyong Liang;Tingxian Zhang;H. Guan;Qi Lu;J. Xiao;Shao-long Chen;Yao Huang;Yong-Hui Zhang;Cheng-bin Li;Y. Zou;Jiguang Li;Zong-Chao Yan;A. Derevianko;M. Zhan;T. Shi;K. Gao
高电荷态离子（HCI）由于其紧密束缚的电子云，可以显著抑制环境对量子振荡器的干扰，是下一代原子钟的理想候选者。在这里，我们提出并追求一个实验策略，同时专注于一个单一的原子元素的各种HCI，保持尽可能大的候选时钟转换的数量。根据这一策略，我们确定了四个相邻的镍HCl的电荷状态，提供多达六个光学跃迁。在实验上，我们证明了在低能量紧凑的上海-武汉电子束离子阱中产生这些离子的基本能力。我们测量了四个磁偶极（$M$1）和一个电四极（$E$2）时钟跃迁的波长，精确度为几个ppm，采用一种新的校准方法;其中两条线首次在受控实验室环境中观察和表征。与早期的测定相比，我们的测量将波长精度提高了一个数量级。这样的测量对于限制激光波长范围以找到“大海捞针”的窄线至关重要。此外，我们还计算了频率和品质因子，评估了这六个跃迁对基础物理应用所需的电磁精细结构常数$\alpha$的假设变化的敏感性。我们认为，镍HCI中的所有六个跃迁都对量子振荡器的所有常见扰动提供了固有的免疫力，其中一个跃迁的投影分数频率不确定度下降到10$^{-19}$的显著水平。
Highly charged ions (HCIs) are promising candidates for the next generation of atomic clocks, owing to their tightly bound electron cloud, which significantly suppresses the common environmental disturbances to the quantum oscillator. Here we propose and pursue an experimental strategy that, while focusing on various HCIs of a single atomic element, keeps the number of candidate clock transitions as large as possible. Following this strategy, we identify four adjacent charge states of nickel HCIs that offer as many as six optical transitions. Experimentally, we demonstrated the essential capability of producing these ions in the low-energy compact Shanghai-Wuhan Electron Beam Ion Trap. We measured the wavelengths of four magnetic-dipole ($M$1) and one electric-quadrupole ($E$2) clock transitions with an accuracy of several ppm with a novel calibration method; two of these lines were observed and characterized for the first time in controlled laboratory settings. Compared to the earlier determinations, our measurements improved wavelength accuracy by an order of magnitude. Such measurements are crucial for constraining the range of laser wavelengths for finding the"needle in a haystack"narrow lines. In addition, we calculated frequencies and quality factors, evaluated sensitivity of these six transitions to the hypothetical variation of the electromagnetic fine structure constant $\alpha$ needed for fundamental physics applications. We argue that all the six transitions in nickel HCIs offer intrinsic immunity to all common perturbations of quantum oscillators, and one of them has the projected fractional frequency uncertainty down to the remarkable level of 10$^{-19}$.