Summary form only given, as follows.Single /sup 171/Yb ions are laser cooled in a Paul trap, using laser sources based on semiconductor diode lasers. Excitation of the potential frequency-standard reference transition to the /sup 2/D/sub 3/2/, (F=2) hyperfine sublevel of /sup 171/Yb/sup +/ at a wavelength of 435.5 nm is demonstrated.
We describe experimental investigations of an optical frequency standard based on a single laser-cooled /sup 171/Yb/sup +/ ion confined in a radiofrequency Paul trap. The electric quadrupole transition from the /sup 2/S/sub 1/2 /(F=0) ground state to the /sup 2/D/sub 3/2/(F=2) state at 435.5 nm is used as the reference transition. The transition was resolved with a Fourier-limited width of approximately 30 Hz. In order to investigate the instability and accuracy of a future frequency standard based on the reference transition, a first experiment was done comparing two laser frequencies stabilized individually to two separate ions in different traps. As a result we found a relative frequency instability /spl sigma//sub y/(640 s)=1.5/spl middot/10/sup -15/ for the difference of the two laser frequencies. We also derived a first estimate /spl Theta/(/sup 2/D/sub 3/2/)=(3.9/spl plusmn/1.9)ea/sub 0//sup 2/ for the electric quadrupole moment of the /sup 2/D/sub 3/2/ state.
A single laser cooled ion in a radiofrequency trap can serve as the basis for a highly stable optical frequency standard. We present recent results of our work on single indium ions, using the /sup 1/S/sub 0/ to /sup 3/P/sub 0/ transition at 236.5 nm wave-length as the clock transition. This resonance has a linewidth of only 0.82 Hz where systematic shifts should be controllable on the mHz level. A single In/sup +/ ion is stored in a miniature Paul-Straubel trap and laser cooled to a temperature of about 100 /spl mu/K. The clock transition is excited using a frequency quadrupled Nd:YAG laser. A fractional resolution of 1.3/spl middot/10/sup -13/ has been achieved so far (linewidth of 170 Hz at 1267 THz). The absolute frequency of the clock transition clock transition has been measured with an uncertainty of 2/spl middot/10/sup -13/ using a frequency chain and a methane-stabilized HeNe laser as a reference, that was calibrated with a cesium clock.