Atomic Physics
When collecting spectroscopic data on at least four isotopes, nonlinearities in the King plot are a possible sign of Physics beyond the Standard Model. In this work, an improved approach to the search for hypothetical new interactions with…
We search for ultralight scalar dark matter candidates that induce oscillations of the fine structure constant, the electron and quark masses, and the quantum chromodynamics energy scale with frequency comparison data between an $^{171}$Yb…
The energy shift in molecular spectra due to interaction of nuclear magnetic quadrupole moment ($M$) with electrons is equal to $\delta E_M = MW_M P_{ M}$, where $W_M$ is a constant determined by the electronic structure of the molecule and…
Experimental searches for new, "fifth" forces are attracting a lot of attention because they allow to test theoretical extensions to the standard model. Here, we report a new experimental search for possible fifth forces, specifically…
Alkaline-earth-like~(AEL) atoms with two valence electrons and a nonzero nuclear spin can be excited to Rydberg state for quantum computing. Typical AEL ground states possess no hyperfine splitting, but unfortunately a GHz-scale splitting…
The optical emission spectrum of acetylene excited by monoenergetic electrons was studied in the range of 190 nm to 660 nm. The dissociative excitation and dissociative ionization associated with excitation of the ions initiated by electron…
We study ionization of atoms in strong elliptically-polarized laser fields. We focus on the physical origin of the offset angle in the photoelectron momentum distribution and its possible relation to a specific time. By developing a model…
Theories that extend the Standard Model of particle physics often introduce new interactions that violate charge-parity (CP) symmetry. CP-violating effects within an atomic nucleus can be probed by measuring its nuclear magnetic quadrupole…
Cryogenic buffer gas beams are central to many cold molecule experiments. Here, we use absorption and fluorescence spectroscopy to directly compare molecular beams of AlF, CaF, MgF, and YbF molecules, produced by chemical reaction of laser…
The Rydberg formula along with the Ritz quantum defect ansatz has been a standard theoretical tool used in atomic physics since before the advent of quantum mechanics, yet this approach has remained limited by its non-relativistic…
The nondirect product discrete variable representation (npDVR) is developed for the time-dependent Schr\"odinger equation with nonseparable angular variables and is applied to a hydrogen atom in elliptically polarized strong laser fields.…
We demonstrate a tuneable, chip-scale wavelength reference to greatly reduce the complexity and volume of cold-atom sensors. A 1 mm optical path length micro-fabricated cell provides an atomic wavelength reference, with dynamic frequency…
Active optical frequency standards provide interesting alternatives to their passive counterparts. Particularly, such a clock alone continuously generates highly-stable narrow-line laser radiation. Thus a local oscillator is not required to…
Ultracold molecules undergo "sticky collisions" that result in loss even for chemically nonreactive molecules. Sticking times can be enhanced by orders of magnitude by interactions that lead to non-conservation of nuclear spin or total…
One of the most enduring and intensively studied problems of X-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed…
We have made the first absolute, reference-free measurement of the 1s2s 3 S1 $\rightarrow$ 1s 2 1 S0 relativistic magnetic dipole transition in He-like sulfur. The highly-charged S ions were provided by an electron-cyclotron resonance ion…
We revisit the photoabsorption from the ground state of Na, ending below and above the ionization threshold, with special emphasis on the shape of the photoionization cross section around the Cooper minimum. The present treatment, using a…
We study single-photon ionization of aligned H$_2^+$ in a high-frequency low-intensity laser field. We focus on the case where the laser frequency is not far larger than the ionization potential of the target. The calculated photoelectron…
We propose a continuous variable quantum state tomography protocol of electrons which result from the ionization of atoms or molecules by the absorption of extreme ultraviolet light pulses. Our protocol is benchmarked against a direct…
A universal mechanism of ultrafast two-electron orbital swap is discovered through two-photon sequential double ionization of Li. After a $1s$ electron in Li is ionized by absorbing an EUV photon, the other two bound electrons located on…