Precision determination of the ground-state hyperfine splitting of trapped 113Cd+ ions

We measured the ground-state hyperfine splitting of trapped 113Cd+ ions to be 15199862855.02799(27) Hz with a fractional uncertainty of 1.8×10−14. The ions were trapped and laser-cooled in a linear quadrupole Paul trap. The fractional frequency stability was measured to be ..., obtained from Ramsey fringes of high signal-to-noise ratios and taken over a measurement time of nearly 5 h, which is close to the short-term stability limit estimated from the Dick effect. Our result is consistent with previously reported values, but the measurement precision is four times better than the best result obtained to date.