Lange R, Huntemann N, Rahm J M, Sanner C, Shao H, Lipphardt B, Tamm Chr, Weyers S, Peik E
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
Phys Rev Lett. 2021 Jan 8;126(1):011102. doi: 10.1103/PhysRevLett.126.011102.
We compare two optical clocks based on the ^{2}S_{1/2}(F=0)→^{2}D_{3/2}(F=2) electric quadrupole (E2) and the ^{2}S_{1/2}(F=0)→^{2}F_{7/2}(F=3) electric octupole (E3) transition of ^{171}Yb^{+} and measure the frequency ratio ν_{E3}/ν_{E2}=0.932829404530965376(32), improving upon previous measurements by an order of magnitude. Using two caesium fountain clocks, we find ν_{E3}=642121496772645.10(8) Hz, the most accurate determination of an optical transition frequency to date. Repeated measurements of both quantities over several years are analyzed for potential violations of local position invariance. We improve by factors of about 20 and 2 the limits for fractional temporal variations of the fine structure constant α to 1.0(1.1)×10^{-18}/yr and of the proton-to-electron mass ratio μ to -8(36)×10^{-18}/yr. Using the annual variation of the Sun's gravitational potential at Earth Φ, we improve limits for a potential coupling of both constants to gravity, (c^{2}/α)(dα/dΦ)=14(11)×10^{-9} and (c^{2}/μ)(dμ/dΦ)=7(45)×10^{-8}.
我们基于(^{171}Yb^{+})的(^{2}S_{1/2}(F = 0)→^{2}D_{3/2}(F = 2))电四极（E2）跃迁和(^{2}S_{1/2}(F = 0)→^{2}F_{7/2}(F = 3))电八极（E3）跃迁比较了两个光钟，并测量了频率比(ν_{E3}/ν_{E2}=0.932829404530965376(32))，比之前的测量精度提高了一个数量级。使用两台铯喷泉钟，我们得到(ν_{E3}=642121496772645.10(8))Hz，这是迄今为止对光跃迁频率最精确的测定。对这两个量在数年中的重复测量进行了分析，以寻找可能违反局部位置不变性的情况。我们将精细结构常数(α)的分数时间变化极限提高了约20倍，至(1.0(1.1)×10^{-18}/yr)，将质子与电子质量比(μ)的分数时间变化极限提高了2倍，至(-8(36)×10^{-18}/yr)。利用太阳在地球处引力势(Φ)的年变化，我们改进了这两个常数与引力潜在耦合的极限，((c^{2}/α)(dα/dΦ)=14(11)×10^{-9})和((c^{2}/μ)(dμ/dΦ)=7(45)×10^{-8})。
