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

We present new measurements of quantum defects and core polarizabilities in cesium (${}^{133}$Cs), based on transition frequency measurements between Rydberg states ($14\le n\le 38$) 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 $s_{1\mathrm{/}2}$, $p_{1\mathrm{/}2}$, $p_{3\mathrm{/}2}$, $d_{3\mathrm{/}2}$, $d_{5\mathrm{/}2}$, $f_{5\mathrm{/}2}$, $f_{7\mathrm{/}2}$, $g_{7\mathrm{/}2}$ and $g_{9\mathrm{/}2}$ electronic states. Transitions between high angular momentum states ($4\le \mathrm{\ell }\le 8$) 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 $n{\mathrm{\ell }}_j$ Rydberg states can be estimated to a precision of a few MHz or less.