Ultra precise determination of Cs($nS_{1/2}$) and Cs($nD_J$) quantum defects for sensing and computing: Evaluation of core contributions

TL;DR

This paper reports ultra-precise measurements of cesium Rydberg states, providing the most accurate quantum defect parameters to date, which enhance the understanding of atomic structure for sensing and computing applications.

Contribution

The study presents the most precise quantum defect measurements for Cs Rydberg states and clarifies the series termination, improving atomic models for quantum technologies.

Findings

Quantum defect parameters are the most precise to date.

Series termination at δ₄ is confirmed, refining previous models.

Predictions of Rydberg transition properties match advanced calculations.

Abstract

We make absolute frequency measurements of Cs Rydberg transitions, $\vert 6S_{1/2}, F=3 \rangle \rightarrow \vert nS_{1/2}~(n=23\rm{-}90)\rangle$ and $\vert nD_{3/2,5/2}~(n=21\rm{-}90)\rangle$, with an accuracy of less than $ 72\,\rm kHz$. The quantum defect parameters for the measured Rydberg series are the most precise obtained to date. The quantum defect series is terminated at $\delta_4$, showing that prior fits requiring higher order quantum defects reflect uncertainties in the observations. The precision of the measured quantum defects allow for the calculation of Rydberg electric-dipole transitions and fine-structure intervals extrapolated from high principal quantum numbers, to rival that of sophisticated many-body relativistic calculations carried out at low Rydberg principal quantum numbers. We quantitatively predict the contributions to the quantum defect parameters from core polarization and core penetration of Cs inner shell electrons. A new value for the ionization energy, consistent across the $ nS_{1/2}$ and $ nD_{3/2,5/2}$ Rydberg series, is reported at $31406.467 751 48 (14)~\rm{cm}^{-1}$.