Experimental Determination (similar to mHz) of the Ground-State Hyperfine Separation of Trapped Hg-199(+) in a Hyperbolic Paul Trap

The Ramsey fringes on the ground-state hyperfine transition of Hg-199(+) (Delta F = 1, Delta m(F) = 0) ions trapped in a hyperbolic Paul trap are firstly observed with the method of time-separated oscillatory fields. The full width at half maximum of central Ramsey fringes is about 25mHz and the corresponding quality factor Q of the line is greater than 10(12) for the trapped Hg-199(+) microwave frequency standard. The hyperfine transition frequency shifted by magnetic field is also measured by the high-resolution Ramsey fringes. The final result is Delta nu(hfs) = 40507347997.3(0.5) Hz, which is corrected to zero magnetic field.