High-performance trapped Hg/sup +/ frequency standards

We have demonstrated a new frequency standard, accurate to 3.4/spl times/10/sup -15/, based on the 40.5 GHz ground state hyperfine transition in cooled and trapped /sup 199/Hg/sup +/. We are also developing an optical frequency standard based on /sup 199/Hg/sup +/. The spectral width of the 563 nm laser used in this standard is less than 6 Hz.