Chen Yihe

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.

Microwave-Optical Double-Resonance Spectroscopy Experiment of 199Hg+ Ground State Hyperfine Splitting in a Linear Ion Trap

We report a spectroscopy experiment of the Hg-199(+) ground state hyperfine splitting in a linear ion trap. The ions are optically pumped by a discharge lamp and cooled by helium buffer gas. The ground state hyperfine splitting is measured to be 40507347996.8(0.1) Hz by the microwave-optical double-resonance method. A narrow line width as 30 mHz is also observed. This progress builds the foundation for the realization of trapped Hg-199(+) ion frequency standards.

Comparison experiments of neon and helium buffer gases cooling in trapped Hg-199(+) ions linear trap

The influences of different buffer gas, neon and helium, on Hg-199(+) clock transition are compared in trapped Hg-199(+) linear trap. By the technique of time domains Ramsey separated oscillatory fields, the buffer gas pressure frequency shifts of Hg-199(+) clock transition are measured to be (df/dP(Ne)) (1/f) = 1.8 x 10(-8) Torr(-1) for neon and (df/dP(He)) (1/f) = 9.1 x 10 8 Torr(-1) for helium. Meanwhile, the line-width of Hg-199(+) clock transition spectrum with the buffer gas neon is narrower than that with helium at the same pressure. These experimental results show that neon is a more suitable buffer gas than helium in Hg-199(+) ions microwave frequency standards because of the Hg-199(+) clock transition is less sensitive to neon variations and the better cooling effect of neon. The optimum operating pressure for neon is found to be about 1.0 x 10(-5) Torr in our linear ion trap system.

A Method of Measuring the Axial Secular Motion Temperature of Trapping Large Size Ion Clouds

A large cloud of Ca-40(+) is successfully trapped and manipulated in a linear ion trap. The axial length of the ion cloud is measured under a series of end-cap voltages. We propose a method of measuring the axial secular motion temperature of the ion cloud by analyzing its image on an electron-multiplying CCD. The method is based on the Boltzmann equation that the axial density distribution of ions at secular motion temperature T satisfies. The axial secular motion temperature of the ion cloud is also obtained by measuring the Doppler broadened line width. For the same trapping parameters, the axial secular motion temperature by analyzing the image of ion cloud is 840 K and by fitting the experimental resonance line profile is 700 K.