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تسجيل مستخدم جديدImproved limit on a temporal variation of $m_p/m_e$ from comparisons of Yb$^+$ and Cs atomic clocks
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Accurate measurements of different transition frequencies between atomic levels of the electronic and hyperfine structure over time are used to investigate temporal variations of the fine structure constant $alpha$ and the proton-to-electron mass ratio $mu$. We measure the frequency of the $^2S_{1/2}rightarrow {^2F_{7/2}}$ electric octupole (E3) transition in $^{171}$Yb$^+$ against two caesium fountain clocks as $f(E3) = 642,121,496,772,645.36(25)$~Hz with an improved fractional uncertainty of $3.9times 10^{-16}$. This transition frequency shows a strong sensitivity to changes of $alpha$. Together with a number of previous and recent measurements of the $^2S_{1/2}rightarrow {^2D_{3/2}}$ electric quadrupole transition in $^{171}$Yb$^+$ and with data from other elements, a least-squares analysis yields $(1/alpha)(dalpha/dt)=-0.20(20)times 10^{-16}/mathrm{yr}$ and $(1/mu)(dmu/dt)=-0.5(1.6)times 10^{-16}/mathrm{yr}$, confirming a previous limit on $dalpha/dt$ and providing the most stringent limit on $d mu/dt$ from laboratory experiments.
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We compare two optical clocks based on the $^2$S$_{1/2}(F=0)to {}^2$D$_{3/2}(F=2)$ electric quadrupole (E2) and the $^2$S$_{1/2}(F=0)to {}^2$F$_{7/2}(F=3)$ electric octupole (E3) transition of $^{171}$Yb$^{+}$ and measure the frequency ratio $ u_{mat
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