Single-ion optical frequency standards and measurement of their absolute optical frequency

This work examines the current status of research on optical frequency standards based upon single trapped ions, Methods for the containment and laser cooling of such single-ion samples are briefly discussed. Detection of ultra-narrow reference transitions via the observation of quantum jumps is outlined, together with the progress in the development of laser sources to provide cooling, detection and probing for such standards. A brief discussion on methods employed to date on stabilization to single-ion transition resonances is given, together with a summary of some of the principal sources fur systematic shifts in such systems. Progress in the investigation of Ba+, Sr+, Ca+, Hg+, Yb+, and In+ single-ion reference transitions is given. The work concludes with an overview of the progress in the measurement of single-ion referenced optical frequency relative to the Cs realization of the SI second and other reference standards.