A laser optical-pumping, double-resonance experiment was performed on electrodynamically confined
171Yb+ ions. The ground-state hyperfine splitting has been determined to be $\ensuremath{\Delta}{W}_{\mathrm{h}\mathrm{f}\mathrm{s}}=12642812124.2\ifmmode\pm\else\textpm\fi{}1.4$ Hz. The ultimate linewidth obtained in this experiment was 60 mHz, corresponding to a line
Q of 0.2\ifmmode\times\else\texttimes\fi{}
1012. It was limited by the stability of the available frequency reference.
The authors report preliminary results of precision microwave-optical double resonance spectroscopy on buffer gas cooled /sup 171/Yb/sup +/ ions confined in a linear Paul trap as a microwave frequency standard at 12.6 GHz. They also report laser cooling of trapped /sup 171/Yb/sup +/ ions. Temperatures below 1 K have been achieved, and evidence for a phase transition to a crystal-like state has been found. This temperature is sufficiently low to reduce the fractional second-order Doppler shift of the microwave resonance to below 10/sup -14/.>