441 research outputs found
High-accuracy optical clock based on the octupole transition in 171Yb+
We experimentally investigate an optical frequency standard based on the 467
nm (642 THz) electric-octupole reference transition 2S1/2(F=0) -> F7/2(F=3) in
a single trapped 171Yb+ ion. The extraordinary features of this transition
result from the long natural lifetime and from the 4f136s2 configuration of the
upper state. The electric quadrupole moment of the 2F7/2 state is measured as
-0.041(5) e(a0)^2, where e is the elementary charge and a0 the Bohr radius. We
also obtain information on the differential scalar and tensorial components of
the static polarizability and of the probe light induced ac Stark shift of the
octupole transition. With a real-time extrapolation scheme that eliminates this
shift, the unperturbed transition frequency is realized with a fractional
uncertainty of 7.1x10^(-17). The frequency is measured as 642 121 496 772
645.15(52) Hz.Comment: 5 pages, 4 figure
Interrogation of caesium atoms in a fountain clock by a femtosecond laser microwave oscillator
A caesium fountain clock is operated utilizing a microwave oscillator that
derives its frequency stability from a stable laser by means of a fiber-laser
femtosecond frequency comb. This oscillator is based on the technology
developed for optical clocks and replaces the quartz based microwave oscillator
commonly used in fountain clocks. As a result, a significant decrease of the
frequency instability of the fountain clock is obtained, reaching 0.74E-14 at
100 s averaging time. We could demonstrate that for a significant range of
detected atom numbers the instability is limited by quantum projection noise
only, and that for the current status of this fountain clock the new microwave
source poses no limit on the achievable frequency instability.Comment: 4 pages, 4 figure
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