The complex Rydberg structure of ytterbium atoms is shaped by multiple low-lying ion-core-excited states and strong channel interactions, which presents both opportunities and challenges for quantum information processing and precision metrology. In this work, we extend high-resolution microwave spectroscopy and multichannel quantum defect theory (MQDT) modeling of singly excited $6sn\ensuremath{\ell}$ Rydberg states in
174Yb and
171Yb to include the $\ensuremath{\ell}=3$ (
f) and $\ensuremath{\ell}=4$ (
g) series. Our measurements reveal $p\text{\ensuremath{-}}f$ mixing in odd-parity Rydberg states of
171Yb, which we incorporate by combined MQDT models for
6snp and
6snf series. Additionally, we observe that for $\ensuremath{\ell}=4$ the spin-orbit interaction dominates over the exchange interaction, such that the
6sng states are more accurately described in a
jj-coupled basis. We validate our models by comparing the predicted Land\'e
g factors and static dipole polarizabilities with experimental measurements, finding excellent agreement. These results provide important input for designing high-fidelity entangling gates with ytterbium atoms.
We utilize two-photon, high-precision microwave spectroscopy of $ng\ensuremath{\rightarrow}(n+2)g$ transitions to precisely measure the high-angular-momentum
g-series quantum defect of
85Rb. Samples of cold Rydberg atoms in the
ng state are prepared via a three-photon optical excitation combined with controlled electric-field mixing and probed with 40-$\ensuremath{\mu}\mathrm{s}$-long microwave interaction pulses. The leading systematic uncertainty arises from DC Stark shifts, which is addressed by a cancellation of background electric fields in all three dimensions. From our measurements and an analysis of systematic uncertainties from DC and AC Stark shifts, van der Waals interactions, and microwave frequency calibration, we obtain ${\ensuremath{\delta}}_{0}=0.003\phantom{\rule{0.16em}{0ex}}999\phantom{\rule{0.16em}{0ex}}0(21)$ and ${\ensuremath{\delta}}_{2}=\ensuremath{-}0.0202(21)$. We discuss our results in context with recent work elsewhere, as well as applications towards precision measurement.
We present precise measurements of the quantum defects of cesium
nFJ Rydberg levels. We employ high-precision microwave spectroscopy of $(n+2){D}_{5/2}\ensuremath{\rightarrow}n{F}_{5/2,7/2}$ transitions for
n=45 to 50 in a cold-atom setup. Cold cesium
(n+2)D5/2 atoms, prepared via two-photon laser excitation, are probed by scanning weak microwave fields interacting with the atoms across the
nF5/2,7/2 resonances. Transition spectra are acquired using state-selective electric-field ionization and time-gated ion detection. Transition-frequency intervals are obtained by Lorentzian fits to the measured spectral lines, which have linewidths ranging between 70 and 190 kHz, corresponding to about one to three times the Fourier limit. A comprehensive analysis of relevant line-shift uncertainties and line-broadening effects is conducted. We find quantum defect parameters ${\ensuremath{\delta}}_{0}({F}_{5/2})=0.033\phantom{\rule{0.16em}{0ex}}415\phantom{\rule{0.16em}{0ex}}37(70)$ and ${\ensuremath{\delta}}_{2}({F}_{5/2})=\ensuremath{-}0.2014(16)$, as well as ${\ensuremath{\delta}}_{0}({F}_{7/2})=0.033\phantom{\rule{0.16em}{0ex}}564\phantom{\rule{0.16em}{0ex}}6(13)$ and ${\ensuremath{\delta}}_{2}({F}_{7/2})=\ensuremath{-}0.2052(29)$, for
J=5/2 and
7/2, respectively. Fine-structure parameters
AFS and
BFS for Cs
nFJ are also obtained. Results are discussed in context with previous works, and the significance of the results is discussed.