We have performed hyperfine spectroscopy of two transitions in ground-state deuterium and searched for violations of CPT and Lorentz symmetry that would manifest as sidereal variations of the observed transition frequencies. Several nonrelativistic proton coefficients of the Standard-Model extension framework have been addressed. The spin-independent coefficients with momentum power k=2, 4 are constrained for the first time. Bounds on spin-dependent coefficients are improved by exploiting a sensitivity enhancement originating from the relative momenta of the nucleons in the deuteron. The best previous constraints by hydrogen maser measurements are surpassed by 4 and 14 orders of magnitude for coefficients with k=2 and 4, respectively.

This study explores the excitation and ionization of an atomic beam as a pathway to optimize focused ion beams (FIBs) for high-precision applications. Leveraging the unique advantages of Rydberg excitation followed by field ionization – specifically its ability to minimize velocity and position dispersions – we present a method to generate ion beams with good performance at low energies. A custom Lua program, integrated into the SIMION simulation platform, models the intricate processes of particle distributions, laser excitation, and Rydberg ionization. This integrated approach incorporates essential parameters such as excitation and ionization rates, Stark shifts, Doppler effects, and electric fields, enabling a detailed analysis of ion beam properties. Our simulations demonstrate the influence of critical factors such as the chosen Rydberg state, ionization region characteristics, and velocity dispersions on the final ion beam quality. By optimizing these parameters, we achieve significant reduction of the axial energy spread and the longitudinal extent of the ionization region. This framework bridges theoretical modeling and experimental validation, offering a comprehensive toolkit for the development of next-generation ion sources and advancing FIB technologies across various scientific domains.

The existence of cosmic fields made from yet unknown light bosons is predicted in many extensions to the Standard Model. They are especially of interest as possible constituents of dark matter. To detect such light and weakly interacting fields, atomic precision measurements offer one of the most sensitive platforms. In this work, we derive which atomic observables are sensitive to what kind of cosmic field couplings. For this we consider fields that couple either through scalar, pseudoscalar, vector, axial vector, or tensor couplings. We derive the corresponding non relativistic atomic potentials. Based on their symmetry properties, these can induce direct energy shifts or induce atomic electric dipole, magnetic dipole, electric quadrupole as well as nuclear Schiff and anapole moments.

This study explores the excitation and ionization of an atomic beam as a pathway to optimize focused ion beams (FIBs) for high-precision applications. Leveraging the unique advantages of Rydberg excitation followed by field ionization-specifically its ability to minimize velocity and position dispersions-we present a method to generate ion beams with good performance at low energies. A custom LUA program, integrated into the simion simulation platform, models the intricate processes of particle distributions, laser excitation, and Rydberg ionization. This integrated approach incorporates essential parameters such as excitation and ionization rates, Stark shifts, Doppler effects, and electric fields, enabling a detailed analysis of ion-beam properties. Our simulations demonstrate the influence of critical factors such as the chosen Rydberg state, ionization region characteristics, and velocity dispersions on the final ion-beam quality. By optimizing these parameters, we achieve significant reduction of the axial energy spread and the longitudinal extent of the ionization region. This framework bridges theoretical modeling and experimental validation, offering a comprehensive toolkit for the development of next-generation ion sources and advancing FIB technologies across various scientific domains.

We report on a Q-switched alexandrite based- 100 ns long pulse duration ultra-violet laser system. The central wavelength of the fundamental pulse is set by a Volume Bragg Grating in reflection and can be tuned between 728 nm and 742 nm. The spectral bandwidth is- 130 GHz. This laser system was designed in view of Doppler cooling of a cloud of a near room temperature positronium by strongly saturating the 1 3 S- 2 3 P transition. In addition, we report on the development of a KD*P Pockels cell driver designed to both Q-switch the cavity and induce a sharp falling edge of the laser pulse so that the end of the positronium-laser interaction time can be controlled with nanosecond precision.

Searches for violations of the fundamental symmetries of parity P and time reversal T in atomic and molecular systems provide a powerful tool for precise measurements of the physics of and beyond the standard model. In this work, we investigate how these symmetry violations affect the response of atoms and molecules to applied electric and magnetic fields. We recover well-known observables such as the P -odd, T -odd spin-electric field coupling that is used for searches of the electron electric dipole moment or the effect of P -odd, T -even optical rotation in atomic gases. Besides these, we obtain several other possible observables. This includes, in particular, effects that can only be seen when using oscillating or inhomogeneous fields.

Using Resonant Pulsed Rydberg Field-ionization (RPRFI) technique, we generate low-energy electron bunches at high repetition rates. By combining continuous-wave laser excitation with a pulsed electric field, this method selectively ionizes Rydberg-Stark states in cesium atoms, producing sub-ns long electron bunches (down to $\sim 250\:\textrm{ps}$) at a repetition rate of $\sim 10\:\textrm{MHz}$. The method is demonstrated to offer significant advantages in terms of flexibility in the ionization repetition rate and pulse delay adjustments. The RPRFI method holds promise for applications in high-resolution electron microscopy and spectroscopy, potentially for overcoming the limitations of traditional electron sources in terms of brightness and energy spread.

We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 1^{3}S-2^{3}P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 2^{3}P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v_{1D}<3.7×10^{4}  ms^{-1}.

We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 13S−23P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 23P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud’s temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v1D<3.7×104 ms−1. Published by the American Physical Society 2024

We propose to extend coherent laser cooling from narrow-band to broad-band transitions by using trains of ultrashort broadband pulses. We study analytically two possible methods to reduce the momentum spread of a distribution by several units of photon momentum in a single spontaneous emission lifetime. We report on numerical simulations of one-dimensional laser cooling of a two-level system with realistic parameters. The technique introduced here is of high interest for efficient laser cooling of fast species with short lifetime such as positronium.

In the search for clues to the matter-antimatter puzzle, experiments with atoms or molecules play a particular role. These systems allow measurements with very high precision, as demonstrated by the unprecedented limits down to $10^{-30}$ e.cm on electron EDM using molecular ions, and relative measurements at the level of $10^{-12}$ in spectroscopy of antihydrogen atoms. Building on these impressive measurements, new experimental directions offer potentials for drastic improvements. We review here some of the new perspectives in those fields and their associated prospects for new physics searches.

Laser cooling of neutral and positively charged ions is well mastered, but cooling of anions remains largely unexplored. Now, laser-induced evaporative cooling of negatively charged molecules has been achieved.

This paper presents both experimental and theoretical investigations into the spectroscopy of dilute cesium (Cs) atoms within a solid argon (Ar) matrix at cryogenic temperatures. This system is relevant for matrix isolation spectroscopy and in particular for recently proposed methods for investigating phenomena that extend beyond the standard model of particle physics. We record absorption spectra at various deposition temperatures and examine the evolution of these spectra post-deposition with respect to temperature changes. Taking advantage of Cs-Ar and Ar-Ar pairwise interaction potentials, we conduct a stability study of trapping sites, which indicates a preference for T$_{\rm d}$ (tetrahedral, 4 vacancies) and O$_{\rm h}$ (cubic, 6 vacancies) symmetries. By implementing a mean-field analysis of the long-range Cs(6s,6p)-Ar-Ar triple dipole interaction, combined with a temperature-dependent shift in zero point energy, we propose effective Cs(6s,6p)-Ar pairwise potentials. Upon integrating these pairwise potentials with spin-orbit coupling, we achieve a satisfactory agreement between the observed and simulated absorption line positions. The observed line broadening is reasonably well reproduced by a semi-classical thermal Monte Carlo approach based on Mulliken-type differences between excited and ground potential curves. Additionally, we develop a simple, first-order crystal field theory featuring only 6 interaction mode coordinates. It uses the reflection approximation and incorporates quantized (phonon) normal modes. This produces a narrow triplet structure but not the observed amount of splitting.

We present a hybrid imaging/timing detector for force sensitive inertial measurements designed for measurements on positronium, the metastable bound state of an electron and a positron, but also suitable for applications involving other low intensity, low energy beams of neutral (antimatter)-atoms, such as antihydrogen. The performance of the prototype detector was evaluated with a tunable low energy positron beam, resulting in a spatial resolution of approximate to <i 12 mm, a detection efficiency of up to 40% and a time-resolution in the order of tens of ns.

The ability to cool and trap a large number of molecules is currently a crucial challenge for the implementation of various applications in fundamental physics and cold chemistry. We here present an optical cooling of the internal degrees of freedom which maximizes the number of molecules in a minimum number of rotational states. Our demonstration is achieved on a supersonic beam of barium monofluoride seeded in argon, a process that leads to a rotational temperature T rot ≈ 12 K. The rotation is then cooled by our optical pumping to approximately T rot ≈ 0.8 K which, compared to the initial rotational distribution, corresponds to an increase of the number of molecules in the lowest rotational state by one order of magnitude. Our method employs two light sources coming from tapered amplifiers. The first source, dedicated to the rotational cooling of molecules occupying the fundamental vibrational level, is optimized thanks to a spectral shaping whose resolution is comparable to the separation of the relevant rotational levels. The second source is used to pump the molecules back to the fundamental vibrational level when they escape from it. This work focuses on the relevant features of these two types of optical pumping.

We have performed a study of several cesium oven designs. A comparison between recirculating (or sticking-wall) and collimating (or re-emitting-wall) ovens is made in order to extract the most efficient design in terms of beam brightness. Unfortunately, non-reproducible behaviors have been observed, and the most often observed output flux is similar to the sticking-wall case, which is the lowest theoretical value of the two cases, with a beam brightness close to 1018 at. sr-1 s-1 cm-2. The reason of this universally observed behavior is unclear despite having tested several materials for the collimating tube. Conclusion on possible improved design based on sticking of cesium on several (un)cleaned surfaces is given.

We present a Rydberg hydrogen beamline developed to commission techniques of stimulated deexcitation for application in antihydrogen experiments at CERN’s Antiproton Decelerator. The stimulation of spontaneous decay is a key technology to enhance the number of ground-state anti-atoms available in a beam toward precision spectroscopy and gravity measurements.

The primary goal of the AEgIS collaboration at CERN is to measure the gravitational acceleration on neutral antimatter. Positronium (Ps), the bound state of an electron and a positron, is a suitable candidate for a force-sensitive inertial measurement by means of deflectometry/interferometry. In order to conduct such an experiment, the impact position and time of arrival of Ps atoms at the detector must be detected simultaneously. The detection of a low-velocity Ps beam with a spatial resolution of (88 ± 5) μm was previously demonstrated [1]. Based on the methodology employed in [1] and [2], a hybrid imaging/timing detector with increased spatial resolution of about 10 μm was developed. The performance of a prototype was tested with a positron beam. The concept of the detector and first results are presented.

We have performed a 2D blue detuned Sisyphus collimation of a cesium beam. Compared to a red detuned Doppler transverse molasses cooling, the setup was found very advantageous because of its faster cooling time allowing a short ( $${1}~\text {cm}$$ ) cooling length and thus finally a denser atomic beam. A fibered laser was developed delivering up to $${500}\,\text {mW}$$ fiber coupled optical power. A 2D collimation was realized but this can be done only if the two cooling zones were not overlapping. A beam density enhancement of more than 10 was observed. We found that a simple top-hat beam was more efficient than a Gaussian one. Similar cooling applies to other atom species and leads to a simple method to produce bright collimated atomic beams.