Precision determination of the ground-state hyperfine splitting of trapped ${}^{113}$Cd${}^{+}$ ions

TL;DR

This paper reports a highly precise measurement of the hyperfine splitting in trapped ${}^{113}$Cd${}^{+}$ ions, achieving four times better accuracy than previous results, which enhances the potential for precision frequency standards.

Contribution

The study provides the most precise measurement to date of the hyperfine splitting in ${}^{113}$Cd${}^{+}$ ions, improving accuracy by a factor of four over prior work.

Findings

Measured hyperfine splitting: 15199862855.02799(27) Hz

Fractional uncertainty: 1.8×10^{-14}

Achieved fractional frequency stability of 4.2×10^{-13}/√τ

Abstract

We measured the ground-state hyperfine splitting of trapped ${}^{113}$Cd${}^{+}$ ions to be 15199862855.02799(27) Hz with a fractional uncertainty of $1.8\times10^{-14}$. The ions were trapped and laser-cooled in a linear quadrupole Paul trap. The fractional frequency stability was measured to be ${4.2} \times 10^{-13}/\sqrt{\tau} $, obtained from Ramsey fringes of high signal-to-noise ratio and taken over a measurement time of nearly 5 hours, which is close to the short-term stability limit estimated from the Dick effect. Our result is consistent with previous reported values, but the measurement precision is four times better than the best result obtained to date.