Since 1967, the second as the base unit of time in the International System of Units (SI) is
defined via an unperturbed hyperfine transition in atomic caesium [1] that is interrogated by …

We report on the first absolute transition frequency measurement at the 10-15 level with a
single, laser-cooled Ca+ 40 ion in a linear Paul trap. For this measurement, a frequency …

Optical frequency standards based on single trapped ions or ensembles of neutral atoms
have recently demonstrated stability and accuracy superior to that of the current generation …

High-resolution molecular spectroscopy is a sensitive probe for violations of fundamental
symmetries. Symmetry violation searches often require, or are enhanced by, the application …

Optical frequency comparison of the^ 40Ca^+ clock transition ν_Ca (^ 2S_1/2-^ 2D_5/2,
729nm) against the^ 87Sr optical lattice clock transition ν_Sr (^ 1S_0-^ 3P_0, 698nm) has …

We have measured the absolute frequency of a clock transition at the 10− 15 level with a
single, trapped, laser-cooled 40 Ca+ ion in a miniature Paul trap. In our measurement, an …

An absolute frequency measurement has been made of the 2 S 1/2–2 F 7/2 electric octupole
transition in a single ion of 171 Yb+. The implementation of a diode-based probe laser …

We demonstrated transferring the stability of one highly stable clock laser operating at 729
nm to another less stable laser operating at 698 nm. The two different wavelengths were …

The dynamic polarizabilities of the 4 s, 3 d, and 4 p states of Ca+, are calculated using a
relativistic structure model. The wavelengths at which the Stark shifts between different pairs …

Progress on the evaluation of systematic frequency shifts is described in the development of
the optical frequency standard based on single-trapped 40 Ca+ with a “clock” transition at …