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Chinese Physics Letters

Experimental Determination (∼mHz) of the Ground-State Hyperfine Separation of Trapped 199 Hg + in a Hyperbolic Paul Trap

Yue-Hong He, Lei She, Yi-He Chen, Yu-Na Yang, Hao Liu, Jiaomei Li

Published Dec 1, 2012• 6 citations
Publisher

Abstract

The Ramsey fringes on the ground-state hyperfine transition of 199 Hg + (ΔF = 1, Δm F = 0) ions trapped in a hyperbolic Paul trap are firstly observed with the method of time-separated oscillatory fields. The full width at half maximum of central Ramsey fringes is about 25 mHz and the corresponding quality factor Q of the line is greater than 10 12 for the trapped 199 Hg + microwave frequency standard. The hyperfine transition frequency shifted by magnetic field is also measured by the high-resolution Ramsey fringes. The final result is Δν h f s = 40507347997.3(0.5) Hz, which is corrected to zero magnetic field.

DOI
10.1088/0256-307x/29/12/123201

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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 15, 1998•1 citation
The Ramsey fringes on the ground-state hyperfine transition of 199 Hg + (ΔF = 1, Δm F = 0) ions trapped in a hyperbolic Paul trap are firstly observed with the method of time-separated oscillatory fields. The full width at half maximum of central Ramsey fringes is about 25 mHz and the corresponding quality factor Q of the line is greater than 10 12 for the trapped 199 Hg + microwave frequency standard. The hyperfine transition frequency shifted by magnetic field is also measured by the high-resolution Ramsey fringes. The final result is Δν h f s = 40507347997.3(0.5) Hz, which is corrected to zero magnetic field.
Precision measurement of the ground-state hyperfine constant for 9Be+^9Be^+9Be+ in a linear Paul trap via magnetically insensitive hyperfine transitions
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We report an experimental determination of the ground-state hyperfine constant AAA of the 25Mg+^{25}\mathrm{Mg}^{+}25Mg+ ions by measuring the $|{S}_{1/2},F=2,m=0\ensuremath{\rangle}$ to $|{S}_{1/2},F=3,m=0\ensuremath{\rangle}$ transition (0-0 transition) frequency of the two ground-state hyperfine energy levels. The frequency is measured by rf resonant method in a Paul trap under a magnetic field of about 0.1 mT. The result is $A=\ensuremath{-}596.254$ 248 7(42) MHz. Different frequency shifts and uncertainties are evaluated. The main effect is quadratic Zeeman shift. Since the Paul trap is driven by rf on the electrodes, ac magnetic field can be induced by the rf at the site of the ion. The ac magnetic field causes quadratic Zeeman shift for ion frequency standards and also reduces the coherence time when the ion acts as a quantum bit. Precision measurement of this ac magnetic field can help evaluating the related uncertainty when a single-ion optical clock is established on the trap.
We measured the ground-state hyperfine splitting of trapped 113 C d + ions to be 15199862855.02799(27) Hz with a fractional uncertainty of 1.8 × 10 − 14 . The ions were trapped and laser-cooled in a linear quadrupole Paul trap. The fractional frequency stability was measured to be 4.2 × 10 − 13 / τ , obtained from Ramsey fringes of high signal-to-noise ratios and taken over a measurement time of nearly 5 h, which is close to the short-term stability limit estimated from the Dick effect. Our result is consistent with previously reported values, but the measurement precision is four times better than the best result obtained to date.
Direct measurements of the ground-state magnetically insensitive hyperfine transition | F = 2 , m F = 0 〉 → | F = 1 , m F = 0 〉 of Be + 9 ions have been performed using microwave-driven state transfer. The Be + 9 ions are confined and laser cooled in a linear Paul trap, forming a Coulomb crystal. The transition frequencies have been measured over a magnetic-field range of ± 0.5 mT centered at zero magnetic field and the acquired data were fitted accounting for the high-order Zeeman effect. The hyperfine constant A is determined to be − 625.008 840 ( 35 ) MHz, achieving a relative precision of 5.6 × 10 − 8 .
We discuss frequency standards based on laser-cooled 199Hg+ ions confined in cryogenic rf traps. In one experiment, the frequency of a microwave source is served to the ions' ground-state hyperfine transition at 40.5 GHz. For seven ions and a Ramsey free precession time of 100 s, the fractional frequency stability is 3.3 (2) X 10-13 (tau) -1/2 for measurement times (tau) < 2 h. The ground-state hyperfine interval is measured to be 40 507 347 996.841 59 (14) (41) Hz, where the first number in parentheses is the uncertainty due to statistics and systematic errors, and the second is the uncertainty in the frequency of the time scale to which the standard is compared. In a second experiment under development, a strong-binding cryogenic trap will confine a single ion used for an optical frequency standard based on a narrow electric quadrupole transition at 282 nm. The bandwidth of the laser used to drive this transition is less than 10 Hz at 563 nm.