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An optical frequency/wavelength standard using the high line Q/sup 2/S/sub 1/2/-/sup 2/D/sub 5/2/ transition of Ca/sup +/ confined in a RF trap and laser cooled is discussed according to the following points: optical excitation scheme to cool the ions and probe the clock transition of an odd isotope of Ca/sup +/ and feasibility of the production of the optical excitations from laser diodes. >

A frequency control loop which locks the frequency of a 5-MHz quartz crystal oscillator to a value defined by the hyperfine transition of 199Hg+ ions is described. The properties of the closed loop are studied using the z-transform technique. The loop parameters are calculated in order to optimize the response time to some usual deterministic perturbations of the VCXO frequency. The results of this analysis can be applied to other digital control loops, such as the hydrogen-maser auto-tuning system.

A method is described which makes it possible to measure the relaxation time constants of mercury ions. They are confined in a radio-frequency trap and optically pumped in order to observe the hyperfine transition in their ground state. This method is based on the study of the fluorescence signal emitted by the ions in various steady- and transient-state experiments. The storage time, longitudinal and transverse relaxation times, and the optical pumping time are measured.