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

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 ($4 \leq \ell \leq 8$) were measured to extract the Cs$^{+}$ dipole and quadrupole polarizabilities. We find $\alpha_{d} = 15.729(18)$ $a_{0}^{3}$ and $\alpha_{q} = 76.3(1.9)$ $a_{0}^{5}$ respectively. Using these results, and accounting for the covariances between parameters in the global fit, the energies for $n\ell_{j}$ Rydberg states can be estimated to a precision of a few MHz or less.