330 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
A generalized Ramsey excitation scheme with suppressed light shift
We experimentally investigate a recently proposed optical excitation scheme
[V.I. Yudin et al., Phys. Rev. A 82, 011804(R)(2010)] that is a generalization
of Ramsey's method of separated oscillatory fields and consists of a sequence
of three excitation pulses. The pulse sequence is tailored to produce a
resonance signal which is immune to the light shift and other shifts of the
transition frequency that are correlated with the interaction with the probe
field. We investigate the scheme using a single trapped 171Yb+ ion and excite
the highly forbidden 2S1/2-2F7/2 electric-octupole transition under conditions
where the light shift is much larger than the excitation linewidth, which is in
the Hertz range. The experiments demonstrate a suppression of the light shift
by four orders of magnitude and an immunity against its fluctuations.Comment: 5 pages, 4 figure
Atomic clocks with suppressed blackbody radiation shift
We develop a nonstandard concept of atomic clocks where the blackbody
radiation shift (BBRS) and its temperature fluctuations can be dramatically
suppressed (by one to three orders of magnitude) independent of the
environmental temperature. The suppression is based on the fact that in a
system with two accessible clock transitions (with frequencies v1 and v2) which
are exposed to the same thermal environment, there exists a "synthetic"
frequency v_{syn} (v1-e12 v2) largely immune to the BBRS. As an example, it is
shown that in the case of ion 171Yb+ it is possible to create a clock in which
the BBRS can be suppressed to the fractional level of 10^{-18} in a broad
interval near room temperature (300\pm 15 K). We also propose a realization of
our method with the use of an optical frequency comb generator stabilized to
both frequencies v1 and v2. Here the frequency v_{syn} is generated as one of
the components of the comb spectrum and can be used as an atomic standard.Comment: 5 pages, 2 figure
Atomic photoexcitation as a tool for probing purity of twisted light modes
The twisted light modes used in modern atomic physics experiments can be
contaminated by small admixtures of plane wave radiation. Although these
admixtures hardly reveal themselves in the beam intensity profile, they may
seriously affect the outcome of high precision spectroscopy measurements. In
the present study we propose a method for diagnosing such a plane wave
contamination, which is based on the analysis of the magnetic sublevel
population of atoms or ions interacting with the "twisted + plane wave"
radiation. In order to theoretically investigate the sublevel populations, we
solve the Liouville-von Neumann equation for the time evolution of atomic
density matrix. The proposed method is illustrated for the electric dipole transition in
Rb induced by (linearly, radially, or azimuthally polarized) vortex light with
just a small contamination. We find that even tiny admixtures of plane wave
radiation can lead to remarkable variations in the populations of the
ground-state magnetic sublevels. This opens up new opportunities for
diagnostics of twisted light in atomic spectroscopy experiments.Comment: 12 pages, 11 figure
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