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

The influences of different buffer gas, neon and helium, on 199Hg+ clock transition are compared in trapped 199Hg+linear trap. By the technique of time domain's Ramsey separated oscillatory fields, the buffer gas pressure frequency shifts of 199Hg+ clock transition are measured to be (df/dPNe)(1/f) = 1.8 × 10−8 Torr−1 for neon and (df/dPHe)(1/f) = 9.1×10−8 Torr−1 for helium. Meanwhile, the line-width of 199Hg+ 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 199Hg+ ions microwave frequency standards because of the 199Hg+ 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 1.0×10−5 Torr in our linear ion trap system.