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A comprehensive theory of the Lamb shift in light muonic atoms such as $\mu$H, $\mu$D, $\mu^3$He$^+$, and $\mu^4$He$^+$ is presented, with all quantum electrodynamic corrections included at the precision level constrained by the uncertainty…
We present a method for accurate determination of atomic transition matrix elements at the 10^{-3} level. Measurements of the ac Stark (light) shift around "magic-zero" wavelengths, where the light shift vanishes, provide precise…
The saturated absorption spectrum of the hyperfine-less S(0) quadrupole line in the (2-0) band of H$_2$ is measured at $\lambda=1189$ nm, using the NICE-OHMS technique under cryogenic conditions (72~K). It is for the first time that a Lamb…
The hyperfine (hf) transition rates for muonic atoms have been re-measured for select light nuclei, using neutron detectors to evaluate the time dependence of muon capture. For $^{19}$F $\Lambda$$_{h}$ = 5.6 (2) $\mu$s$^{-1}$ for the hf…
Precision spectroscopy of light muonic atoms provides unique information about the atomic and nuclear structure of these systems and thus represents a way to access fundamental interactions, properties and constants. One application…
We present new investigation of the Lamb shift (2P_{1/2}-2S_{1/2}) in muonic deuterium (mu d) atom using the three-dimensional quasipotential method in quantum electrodynamics. The vacuum polarization, nuclear structure and recoil effects…
Should muon-to-electron conversion in the field of a nucleus be found in the current generation of experiments, the measurement of the atomic number dependence of the process will become an important experimental goal. We present a new…
We have completed a measurement of the $(6s^26p^2)\, ^3\!P_0 \rightarrow \, ^3\!P_2$ 939 nm electric quadrupole ($E2$) transition amplitude in atomic lead. Using a Faraday rotation spectroscopy technique and a sensitive polarimeter, we have…
In view of the future plans to measure the Lamb shift in muonic Lithium atoms we address the microscopic theory of the $\mu$-$^6$Li$^{2+}$ and $\mu$-$^7$Li$^{2+}$ systems. The goal of the CREMA collaboration is to measure the Lamb shift to…
We consider one-loop light-by-light-scattering contributions to the Lamb shift of the $1s, 2s, 2p$ states in light muonic hydrogen like atoms at $Z\leq10$. The contributions are of the order $\alpha^5m_\mu$ (with diverse dependence on the…
An experiment measuring the 2S Lamb shift in muonic hydrogen mup is being performed at the Paul Scherrer Institute, Switzerland. It requires small and compact detectors for 1.9 keV x rays (2P-1S transition) with an energy resolution around…
We report a precise measurement of the isotope shifts in the $4^2$S$_{1/2} \rightarrow 3^2$D$_{5/2}$ electric quadrupole transition at 729~nm in the $^{40 - 42,44,48}$Ca$^+$. The measurement has been made via high-resolution laser…
The hyperfine splitting of the 5g -> 4f transitions in muonic 185,187-Re has been measured using high resolution HPGe detectors and compared to state-of-the-art atomic theoretical predictions. The spectroscopic quadrupole moment has been…
We present a comprehensive study of the electronic transitions in neutral cadmium (Cd I) with a focus on forbidden transitions, motivated by recent advances in laser technology and the growing relevance of cadmium in quantum gas research,…
The QUARTET collaboration aims to significantly improve the precision of the absolute nuclear charge radii of light nuclei from Li to Ne by using an array of metallic magnetic calorimeters to perform high-precision X-ray spectroscopy of…
Quantum electrodynamics in very strong Coulomb fields is one scope which has not yet been tested experimentally with suffcient accuracy to really determine whether the perturbative approach is valid. One sensitive test is the determination…
We derive a new relation between the observed Lamb shift energies of hydrogen and muonium atoms. The relation is based on the non-relativistic description of the Lamb shift, and the proper treatment of the reduced mass of electron and…
The influence of oscillating quadrupole fields on atomic energy levels is examined theoretically and general expressions for the quadrupole matrix elements are given. The results are relevant to any ion-based clock in which one of the clock…
Laser spectroscopy of the Lamb shift (2S-2P energy difference) in light muonic atoms or ions, in which one negative muon $\mu^-$ is bound to a nucleus, has been performed. The measurements yield significantly improved values of the…
The electronic structure of atomic quantum systems and their dynamical interaction with light is reflected in transition dipole matrix elements coupling the system's energy eigenstates. In this work, we measure phase shifts of the…