Atomic Physics
Methanol radio lines observed in space provide sensitive probes of whether the proton-to-electron mass ratio has changed over cosmic time, but such tests require laboratory rest frequencies with very high accuracy. Here we determine the…
Quantum nonlinear optics by Rydberg polaritons can enable single-photon transistor and switch, single-photon source, and deterministic quantum information processing. A major hindrance in this study is the fast motional decoherence. Here,…
The performance of solid-state $^{229}\text{Th}$ nuclear clocks depends sensitively on the microscopic environment of the thorium nucleus in the host crystal. Here we reassess the dominant quadrupole-split thorium site in…
We present a theoretical study of the higher-order QED contribution to the interelectronic interaction in He- and Li-like ions, where a virtual electron-positron loop is inserted into the photon line of the one-photon exchange diagram. Our…
The energy dependence of the complex phases of electron continuum wave functions carries information about electron dynamics. Streaking and attosecond interference experiments (called RABBIT) seek to measure this energy dependence, and…
Atom interferometry is a sensitive tool for measuring relativistic effects, but there are no known non-trivial exact solutions for relativistic atom interferometer phase shifts. Here we derive relativistically exact expressions within the…
We demonstrate a characterisation methodology for a strontium atomic beam, produced by a two-dimensional magneto-optical trap and delivered via a resonant push beam, using fluorescence spectroscopy and time-of-flight (ToF). This provides…
We measure the spatial pattern associated with the superradiant emission from a cloud of cold 87Rb atoms using Fourier imaging. We observe a highly directional, ring-shaped emission structure, which corresponds to a single collective jump…
Rydberg atoms are highly sensitive to external electric fields due to their exaggerated electronic properties. This unique feature lays the foundation for many of their applications in quantum science. However, an uncontrolled stray…
We investigate the interaction of O$_{2}$ with an X-ray Free Electron laser (XFEL) pulse of short duration. We consider a photon energy of 570 eV, which allows for the formation of molecular states with up to two core holes. We compute the…
In this work, we have investigated the evolution of satellite intensity near the ionization threshold for Cu K-shell transitions through theoretical methods. Employing standard state-of-the-art ab initio methods, we have calculated all Cu…
We report precision measurements of the ratio of Land\'e $g$ factors between the $3^2D_{5/2}$ and $4^2S_{1/2}$ states of a single trapped $^{40}\text{Ca}^+$ ion. The measurements are performed in two distinct ion trap apparatus: a cryogenic…
Hadronic vacuum polarization (hVP) enters simple atomic systems at a level that is small yet decisive for the precision spectroscopy now underway. We evaluate the hVP contributions to the Lamb shift and the hyperfine splitting (HFS) in…
The Stark effect in autoionizing high-$n$ Rydberg states decouples the Rydberg electron from the ion core through $\ell$ mixing with core-nonpenetrating high-$\ell$ states. The Rydberg states become long-lived, which is ideal for precision…
We study the frequency derivatives of selective reflection from high-density rubidium vapor using a hole-burning technique. Saturation dips are observed inside the self-broadened line shapes. The line self-broadening is a combination of…
Exotic helium atoms act as unique atomic traps for heavy, negatively charged particles, protecting them from nuclear annihilation and nuclear capture on timescales long enough to enable high-precision laser spectroscopy. Such measurements…
We report an improved absolute frequency measurement of the $^{176}$Lu$^+\,(^{3}\mathrm{D}_1)$ optical frequency standard, evaluated via a remote link to the NRC-FCs2 caesium fountain primary frequency standard. Operating a single ion clock…
We demonstrate two Doppler-free (DF) excitation schemes for coherent manipulation of the ${}^1\!S_0 - {}^3\!P_0$ clock transition in $^{88}$Sr that achieve microsecond-scale excitation times. The first approach uses three-photon excitation…
Our experimental and numerical study of filamentation of the 248 nm 100 fs pulses in air, nitrogen, and oxygen at atmospheric pressure shows that the densities of photoelectrons in the filaments are not sufficient to limit Kerr…
We develop an analytical framework to constrain Yukawa-type fifth-force interactions using the Lamb shift in hydrogen and deuterium. The sixfold coordinate-space integral for the energy shift is transformed into a one-dimensional…