PROGRESS AT NIST TOWARD ABSOLUTE FREQUENCY STANDARDS USING STORED IONS

Experiments at NIST, whose goal is to realize frequency standards of high accuracy using stored ions, are briefly summarized. In one experiment, an RF oscillator is locked to a nuclear spin-flip hyperfine transition (frequency = 3.03 × 108 Hz) in 9Be+ ions that are stored in a Penning trap and sympathetically laser-cooled. Stability is better than 3 × 10−12 τ−(1/2) and uncertainty in Doppler shifts is estimated to be less than 5 × 10−15. In a second experiment, a stable laser is used to probe an electric quadrupole transition (frequency ≃ 1.07 × 1015 Hz) in a single laser-cooled 199Hg+ ion stored in a Paul trap. The measured Q value of this transition is approximately 1013. Future possible experiments are also discussed. © 1990, IEEE