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

This work examines the current status of research on optical frequency stan dards based upon single trapped ions, Methods for the containment and laser cooling of such single-ion samples are briefly discussed. Detection of ult ra-narrow reference transitions via the observation of quantum jumps is out lined, together with the progress in the development of laser sources to pr ovide cooling, detection and probing for such standards. A brief discussion on methods employed to date on stabilization to single-ion transition reso nances is given, together with a summary of some of the principal sources f ur 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 sing le-ion referenced optical frequency relative to the Cs realization of the S I second and other reference standards.