Precision determination of the excited-state hyperfine splitting of Cadmium ions

TL;DR

This study achieves highly precise measurements of the excited-state hyperfine splitting in cadmium ions, improving uncertainties significantly and providing data crucial for fundamental physics tests and theoretical model validation.

Contribution

It introduces advanced laser and optical comb techniques for precise hyperfine splitting measurements in cadmium ions, surpassing previous accuracy levels.

Findings

Uncertainties reduced to 14.8 kHz and 10.0 kHz.

Estimated magnetic dipole constants for $^{111} ext{Cd}^+$ and $^{113} ext{Cd}^+$.

Measured constants suggest the need for more comprehensive theoretical models.

Abstract

Precision determination of the hyperfine splitting of cadmium ions is essential to study space-time variation of fundamental physical constants and isotope shifts. In this work, we present the precision frequency measurement of the excited-state $^2{P}_{3/2}$ hyperfine splitting of $^{111,113}\mathrm{Cd}^+$ ions using the laser-induced fluorescence technique. By introducing the technology of sympathetic cooling and setting up free-space beat detection unit based on the optical comb, the uncertainties are improved to 14.8 kHz and 10.0 kHz, respectively, two orders of magnitude higher than the reported results from the linear transformation of isotope shifts. The magnetic dipole constants $A_{P_{3/2}}$ of $^{111}\mathrm{Cd}^+$ and $^{113}\mathrm{Cd}^+$ are estimated to be 395 938.8(7.4) kHz and 411 276.0(5.0) kHz, respectively. The difference between the measured and theoretical hyperfine structure constants indicates that more physical effects are required to be considered in the theoretical calculation, and provides critical data for the examination of deviation from King-plot linearity in isotope shifts.