High accuracy measurement of the ground-state hyperfine splitting in a ^113Cd^+ microwave clock

Abstract

A microwave frequency standard based on laser-cooled (113)Cd(+) ions has been developed in recent years, and the short-term frequency instability is measured to be 6.1×10(-13)/√τ. By comparing the Cd(+) clock to a superior frequency reference, the ground-state hyperfine splitting of (113)Cd(+) is measured precisely to be 15199862855.0192(10) Hz with a fractional precision of 6.6×10(-14). This result is consistent with previous results, and the measurement precision is improved by nearly one order more than the best result reported before.

Determination of hyperfine splittings and Landé $g_J$ factors of $5s~^2S_{1/2}$ and $5p~^2P_{1/2,3/2}$ states of $^{111,113}$Cd$^+$ for a microwave frequency standard

“…where J = L + S the total electron angular momentum (S and L the spin and orbital angular momenta), and F = I + J the total angular momentum with I denoting the nuclear spin. In typical conditions of our experiment, B ∼ 8000 nT [15,18]. By introducing values g J = 2.002257 and 1.334056 for the levels 5s 2 S 1/2 and 5p 2 P 3/2 calculated in this work (see text below), the Zeeman shift for the 5s 2 S 1/2 (F = 1)-5p 2 P 3/2 (F = 2) transition of Cd + is estimated to be 0.11 MHz.…”

“…The microwave-frequency standard based on laser-cooled 113 Cd + has achieved an accuracy of 1.8 × 10 −14 and a short-term stability of 4.2×10 −13 / √ τ [15]. The high performance and potential for miniaturization make this frequency standard suitable in establishing a ground-based transportable frequency reference for navigation systems and for comparing atomic clocks between remote sites [15][16][17][18]. Moreover, it has been proposed as a means to achieve an ultra-high level of accuracy down to 10 −15 [19], highlighting the importance of accurately evaluating systematic frequency shifts.…”

Towards a high-performance microwave frequency standard based on ¹¹³Cd⁺ ions

“…Continuous comparison between the Cd + clock and the standard reference gives us a chance to measure the groundstate hyperfine splitting of 113 Cd + with higher precision than before. The measurement results indicates that the measurement precision of the clock transition is improved from 5.3×10 -13 to 6×10 -14 [14].…”

Sympathetic cooling of $^{113}$Cd$^+$ by laser-cooled $^{40}$Ca$^+$ in a linear Paul trap for Microwave Ion Clocks

“…To date, 113 Cd + [10,11], 171 Yb + [12,13], and 199 Hg + [14,15] ions have been used in the development of microwave ion clocks. A great deal of progress has been achieved.…”