Abstract

The ground-state hyperfine transitions of trapped clouds of ⁹Be⁺, ²⁰¹Hg⁺, and ¹⁷¹Yb ions have been made control microwave oscillators.^1-5 The frequency stability of these atomic clocks exceeds that of a primary Cs frequency standard in the short-term regime and that of a hydrogen maser for long times. Systematic perturbations derive from the members of the cloud being placed in an inhomogeneous field and showing residual motion. A single cold ion kept in the field node of an electrodynamic trap lacks these perturbations. The precise control of a standard frequency requires a narrow and weak transition whose resonance can be hardly detected by observation of the fluorescence on this line.

© 1994 Optical Society of America