We numerically evaluate the expected performances of an optical frequency standard at 729 nm based on a single calcium ion. The frequency stability is studied through the Allan deviation and its dependence on the excitation method (single Rabi pulse or two Ramsey pulses schemes) and the laser linewidth are discussed. The minimum Allan deviation that can be expected is estimated to σ y (τ ) ≈ 2.5 × 10 −15 / √ τ with τ the integration time. The frequency shifts induced by the environmental conditions are evaluated to minimize the uncertainty of the proposed standard by chosing the most suited environment for the ion. If using the odd isotope 43 Ca + and a vessel cooled to 77 K, the expected relative shift is −2 × 10 −16 with an uncertainty of ±4 × 10 −16 , mainly due to the quadrupole shift induced by the unknown static electric field gradient .

The lifetime of the 3d 2 D 5/2 -level in singly-ionized calcium has been measured by the electronshelving technique on different samples of rf trapped ions. The metastable state has been directly populated by exciting the dipole-forbidden 4S 1/2 − 3D 5/2 transition. In ion clouds, the natural lifetime of this metastable level has been measured to be (1095±27) ms. For the single-ion case, we determined a lifetime of (1152±20) ms. The 1σ-error bars at the 2%-level have different origins for the two kinds of experiments: data fitting methods for lifetime measurements in an ion cloud and control of experimental parameters for a single ion. De-shelving effects are extensively discussed. The influence of differing approaches for the processing of the single-ion quantum jump data on the lifetime values is shown. Comparison with recent measurements shows excellent agreement when evaluated from a given method.

Single, rf-trapped ions find various applications ranging from metrology to quantum computation. High-resolution interrogation of an extremely weak transition under best observation conditions requires an ion almost at rest. To avoid line-broadening effects such as the second order Doppler effect or rf heating in the absence of laser cooling, excess micromotion has to be eliminated as far as possible. In this work the motional state of a confined three-level ion is probed, taking advantage of the high sensitivity of observed dark resonances to the trapped ion's velocity. Excess micromotion is controlled by monitoring the dark resonance contrast with varying laser beam geometry. The influence of different parameters such as the cooling laser intensity has been investigated experimentally and numerically.