Determination of Quantum Defects and Core Polarizability of Atomic Cesium via Terahertz and Radio-Frequency Spectroscopy in Thermal Vapor

Gianluca Allinson; Lucy A. Downes; Kevin J. Weatherill; C. Stuart Adams

doi:10.1103/PhysRevA.111.062802

paper

Determination of Quantum Defects and Core Polarizability of Atomic Cesium via Terahertz and Radio-Frequency Spectroscopy in Thermal Vapor

arXiv:2502.20961 · doi:10.1103/PhysRevA.111.062802

Abstract

We present new measurements of quantum defects and core polarizabilities in cesium ( $^{133}$ Cs), based on transition frequency measurements between Rydberg states ( $14 \leq n \leq 38$ ) obtained through terahertz (THz) and radio-frequency spectroscopy in a thermal atomic vapor. %By detuning resonant fields coupling neighbouring Rydberg states, we observe a detuning-dependent asymmetry in the line shape which can be used to extract the frequency of the transition. We perform a global fitting of our measurements to extract quantum defects of the $s_{1/2}$ , $p_{1/2}$ , $p_{3/2}$ , $d_{3/2}$ , $d_{5/2}$ , $f_{5/2}$ , $f_{7/2}$ , $g_{7/2}$ and $g_{9/2}$ electronic states. Transitions between high angular momentum states ( $4 \leq ℓ \leq 8$ ) were measured to extract the Cs $^{+}$ dipole and quadrupole polarizabilities. We find $α_{d} = 15.729 (18)$ $a_{0}^{3}$ and $α_{q} = 76.3 (1.9)$ $a_{0}^{5}$ respectively. Using these results, and accounting for the covariances between parameters in the global fit, the energies for $n ℓ_{j}$ Rydberg states can be estimated to a precision of a few MHz or less.

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Precision measurement of Cs( $n F_{J}$ ) quantum defects and calculations of scalar and tensor polarizabilities of the $n S_{1/2}$ , $n P_{J}$ , $n D_{J}$ , and $n F_{J}$ series