Accurate measurement of the 12.6 GHz 'clock' transition in trapped 171Yb+ ions

The frequency of the 171YB+ 12.6 GHz MF = 0 - 0 ground state hyperfine clock transition in buffer gas-cooled ion clouds has ben measured. The ion clouds are confined in two similar linear Paul traps. The frequency of the transition at zero temperature, velocity, electric field and magnetic field was determined to be 12 642 812 118.466 plus or minus 0.002 Hz. The model used is believed to be valid under present operating parameter ranges to within plus or minus 1.5 mHz.