Highly Coherent Spectroscopy of Ultracold Atoms and Molecules in Optical Lattices (original) (raw)
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Precision measurement based on ultracold atoms and cold molecules
AIP Conference Proceedings, 2006
Ultracold atoms and molecules provide ideal stages for precision tests of fundamental physics. With microkelvin neutral strontium atoms confined in an optical lattice, we have achieved a fractional resolution of 4 × 10 −15 on the 1 S 0 − 3 P 0 doubly-forbidden 87 Sr clock transition at 698 nm. The overall systematic uncertainty of the clock is evaluated below the 10 −15 level. The ultrahigh spectral resolution permits resolving the nuclear spin states of the clock transition at small magnetic fields, leading to measurements of the 3 P 0 magnetic moment and metastable lifetime. In addition, photoassociation spectroscopy performed on the narrow 1 S 0 − 3 P 1 transition of 88 Sr shows promise for efficient optical tuning of the ground state scattering length and production of ultracold groundstate molecules. Lattice-confined Sr 2 molecules are suitable for constraining the time-variation of electron-proton mass ratio. In a separate experiment, cold, ground state polar molecules produced from Stark decelerators have enabled an order of magnitude improvement in measurement precision of ground-state, Λ-doublet microwave transitions in the OH molecule. Comparing the laboratory results to those from OH megamasers in interstellar space will allow a sensitivity of 10 −6 for measuring the potential time variation of the fundamental fine structure constant ∆α/α over 10 10 years. These results have also led to improved understandings in the molecular structure. The study of the low magnetic field behavior of OH in its 2 Π 3/2 ro-vibronic ground state precisely determines a differential Landé g-factor between opposite parity components of the Λ-doublet.
Precision spectroscopy of cold strontium atoms, towards optical atomic clock
This report concerns the experiment of precision spectroscopy of cold strontium atoms in the Polish National Laboratory of Atomic, Molecular and Optical Physics in Toruń. The system is composed of a Zeeman slower and magneto-optical traps (at 461 nm and 689 nm), a frequency comb, and a narrow-band laser locked to an ultra-stable optical cavity. All parts of the experiment are prepared and the first measurements of the absolute frequency of the 1 S0-3 P1, 689 nm optical transition in 88 Sr atoms are performed.
Cold atom clocks and applications
Journal of Physics B: Atomic, Molecular and Optical Physics, 2005
This paper describes advances in microwave frequency standards using laser-cooled atoms at BNM-SYRTE. First, recent improvements of the 133 Cs and 87 Rb atomic fountains are described. Thanks to the routine use of a cryogenic sapphire oscillator as an ultra-stable local frequency reference, a fountain frequency instability of 1.6 × 10 −14 τ −1/2 where τ is the measurement time in seconds is measured. The second advance is a powerful method to control the frequency shift due to cold collisions. These two advances lead to a frequency stability of 2 × 10 −16 at 50 000 s for the first time for primary standards. In addition, these clocks realize the SI second with an accuracy of 7 × 10 −16 , one order of magnitude below that of uncooled devices. In a second part, we describe tests of possible variations of fundamental constants using 87 Rb and 133 Cs fountains. Finally we give an update on the cold atom space clock PHARAO developed in collaboration with CNES. This clock is one of the main instruments of the ACES/ESA mission which is scheduled to fly on board the International Space Station in 2008, enabling a new generation of relativity tests.
High-precision measurement of hyperfine structure in theDlines of alkali atoms
Journal of Physics B: Atomic, Molecular and Optical Physics, 2008
We have measured hyperfine structure in the first-excited P state (D lines) of all the naturally-occurring alkali atoms. We use high-resolution laser spectroscopy to resolve hyperfine transitions, and measure intervals by locking the frequency shift produced by an acousto-optic modulator to the difference between two transitions. In most cases, the hyperfine coupling constants derived from our measurements improve previous values significantly.
Physical Review Letters, 2006
We develop a method of spectroscopy that uses a weak static magnetic field to enable direct optical excitation of forbidden electric-dipole transitions that are otherwise prohibitively weak. The power of this scheme is demonstrated using the important application of optical atomic clocks based on neutral atoms confined to an optical lattice. The simple experimental implementation of this method-a single clock laser combined with a dc magnetic field-relaxes stringent requirements in current lattice-based clocks (e.g., magnetic field shielding and light polarization), and could therefore expedite the realization of the extraordinary performance level predicted for these clocks. We estimate that a clock using alkaline-earthlike atoms such as Yb could achieve a fractional frequency uncertainty of well below 10 ÿ17 for the metrologically preferred even isotopes.
A 445-THz (674nm), 88 Sr + trapped and laser cooled single ion reference transition has been used at NRC to extend precision frequency measurements to other points in the electromagnetic (E.M.) spectrum. We are currently refining the single ion experiment to approach the uncertainty limited spectral resolution of 1×10 -15 . Connected with these developments is the use of frequency grids based on mode-locked femtosecond lasers. A band of reference modes extending from 520 nm to beyond 1060 nm has been recently obtained at NRC. With such devices, the possibility of accurate, stable and compact sources at any wavelength is coming into being.
Cold Atom Clocks, Precision Oscillators and Fundamental Tests
Lecture Notes in Physics, 2004
We describe two experimental tests of the Equivalence Principle that are based on frequency measurements between precision oscillators and/or highly accurate atomic frequency standards. Based on comparisons between the hyperfine frequencies of 87 Rb and 133 Cs in atomic fountains, the first experiment constrains the stability of fundamental constants. The second experiment is based on a comparison between a cryogenic sapphire oscillator and a hydrogen maser. It tests Local Lorentz Invariance. In both cases, we report recent results which improve significantly over previous experiments.
Atomic clock with nuclear transition: current status in TU Wien
The nucleus of 229 Thorium presents a unique isomer state of very low energy and long lifetime, current estimates are around 7.8 eV and seconds to hours respectively. This nuclear transitions therefore is a promising candidate for a novel type of frequency standard and severly groups worldwide have set out to investigate this system. Our aim is to construct a "solid state nuclear clock", i.e. a frequency standard where Thorium ions are implanted into Calciumfluoride crystals transparent in vacuum ultraviolet range. As a first step towards an accurate determination of the exact energy and lifetime of this isomer state we perform low-resolution fluorescent spectroscopic measurements.