Spectroscopy Of Atoms Research Articles

Extraction of higher-order radial moments of nuclear charge density from muonic atom spectroscopy

Extraction of higher-order radial moments of nuclear charge density from muonic atom spectroscopy

Probing Polaron Clouds by Rydberg Atom Spectroscopy.

In recent years, Rydberg excitations in atomic quantum gases have become a successful platform to explore quantum impurity problems. A single impurity immersed in a Fermi gas leads to the formation of a polaron, a quasiparticle consisting of the impurity being dressed by the surrounding medium. With a radius of about the Fermi wavelength, the density profile of a polaron cannot be explored using insitu optical imaging techniques. In this Letter, we propose a new experimental measurement technique that enables the insitu imaging of the polaron cloud in ultracold quantum gases. The impurity atom induces the formation of a polaron cloud and is then excited to a Rydberg state. Because of the mesoscopic interaction range of Rydberg excitations, which can be tuned by the principal numbers of the Rydberg state, atoms extracted from the polaron cloud form dimers with the impurity. By performing first principle calculations of the absorption spectrum based on a functional determinant approach, we show how the occupation of the dimer state can be directly observed in spectroscopy experiments and can be mapped onto the density profile of the gas particles, hence providing a direct, real-time, and insitu measure of the polaron cloud.

Free electron laser prepared high-intensity metastable helium and helium-like ions

In the precision spectroscopy of few-electron atoms, the generation of high-intensity metastable helium atoms and helium-like ions is crucial for implementing experimental studies as well as a critical factor for improving the signal-to-noise ratio of experimental measurements. With the rapid development of free-electron laser (FEL) and technology, FEL wavelengths extend from hard X-rays to soft X-rays and even vacuum ultraviolet bands. Meanwhile, laser pulses with ultra-fast, ultra-intense and high repetition frequencies are realized, thus making it possible for FEL to prepare single-quantum state atoms/ions with high efficiency. In this work, we propose an experimental method for obtaining high-intensity single-quantum state helium atoms and helium-like ions by using FEL. The preparation efficiency can be calculated by solving the master equation of light-atom interaction. Considering the experimental parameters involved in this work, we predict that the efficiencies of preparing metastable 2<sup>3</sup>S He, Li<sup>+</sup> and Be<sup>2+</sup> are about 3%, 6% and 2%, respectively. Compared with the common preparation methods such as gas discharge and electron bombardment, a state-of-the-art laser excitation method can not only increase the preparation efficiency, but also reduce the effects of high-energy stray particles such as electrons, ions, and photons generated during discharge. Furthermore, combined with the laser preparation technique, the sophisticated ion confinement technique, which can ensure a long interaction time between the ions and laser, increases the efficiency of metastable Li<sup>+</sup> and Be<sup>2+</sup> by several orders of magnitude. Therefore, the preparation of high-intensity metastable helium and helium-like ions can improve the measurement accuracy of precision spectroscopy of atoms and ions. A new experimental method, based on FEL, to study the fine structure energy levels 2<sup>3</sup>P of helium, has the potential to obtain the results with an accuracy exceeding the sub-kHz level. Thus, the high-precision fine structure constants can be determined with the development of high-order quantum electrodynamics theory. In order to measure energy levels with higher accuracy, a new detection technique, which can reduce or even avoid more systematic effects, must be developed. For example, the quantum interference effect, which has been proposed in recent years, seriously affects the accuracy of fine-structure energy levels. If the interference phenomenon of spontaneous radiation between different excited states can be avoided in the detection process, the measurement accuracy will not be affected by this quantum interference effect. High-intensity metastable atoms or ions in chemical reaction dynamics studies also have better chances to investigate reaction mechanisms. In summary, the FEL preparation of high-intensity metastable helium atoms and helium-like ions proposed in this work will lay an important foundation for developing cold atom physics and chemical reaction dynamics.

Preface to the special topic: Precision spectroscopy of few-electron atoms and molecules

Preface to the special topic: Precision spectroscopy of few-electron atoms and molecules

Prospects for an Active Optical Clock Based on Cavityless Lasing

AbstractActive optical clocks take advantage of the substantial suppression of cavity pulling in the bad‐cavity lasing regime and feature the simple structure and excellent portability. In the extreme case, where the cavity mirror reflection approaches zero and cannot support any quasi‐bound modes for light waves, conventional bad‐cavity lasers become the cavityless lasing and the cavity pulling vanishes. Consequently, the laser frequency is determined entirely by the atomic transition. This work is dedicated to theoretically explore the potential application of the cavityless lasing in active optical clocks. Without loss of generality, Cs atoms with well‐established quantum control techniques are employed as the gain medium that is pumped by a 459‐nm laser. The clock laser wavelength is 1470 nm. The simulation shows that the frequency stability of the clock laser with feasible physical quantities reaches at 1 s of averaging time, one order of magnitude better than the recently demonstrated compact passive optical clocks that are built upon a two‐photon transition in a hot Rb vapor and upon the modulation transfer spectroscopy of thermal Cs atoms. Such compact cavityless lasing‐based active optical clocks have the broad application prospect in satellite navigation and communications and promise an architecture for the integrated photonic metrology.

Experimental perspectives on the matter–antimatter asymmetry puzzle: developments in electron EDM and H¯ experiments

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 potential for drastic improvements. We review here some of the new perspectives in those fields and their associated prospects for new physics searches. This article is part of the theme issue ‘The particle-gravity frontier’.

Photon and Particle Impact Spectroscopy and Dynamics of Atoms, Molecules and Clusters

Photon and Particle Impact Spectroscopy and Dynamics of Atoms, Molecules and Clusters

High resolution spectroscopy of thulium atoms implanted in solid noble gas crystals

High resolution spectroscopy of thulium atoms implanted in solid noble gas crystals

Note on the electromagnetic radius of proton

In this paper, we have analyzed the proton form factor data by using a number of phenomenological parametrizations (models) and extracting the proton electric and magnetic radii. To this end, we performed a global fit to all available form factor data, with the virtual photon momentum squared [Formula: see text] from [Formula: see text] to nearly 10[Formula: see text]GeV2 for electric form factor and from [Formula: see text] to 31[Formula: see text]GeV2 for magnetic one. Special attention was given to the small structure shown by the form factor data near [Formula: see text][Formula: see text]GeV2. It was found that different models yield different structures with different numbers of minimum at this kinematics. Since the slope of form factor in the limit of [Formula: see text] is influenced by this structure, the extracted proton radii are consequently different for different models. Our finding recommends that future experiments should focus on this kinematics instead of low [Formula: see text]. Experimental data with accuracies comparable to those of the latest data at low [Formula: see text] would clearly help to clarify the effect of this structure on the proton charge radius. Interestingly, most of the extracted proton charge radii were found to be closer to the value obtained from the muonic hydrogen atom spectroscopy.

Interference filter based external-cavity diode laser with combined dual interference filters and largely adjustable feedback range

External-cavity diode lasers (ECDL) are widely used as light sources in laser spectroscopy, atomic physics, and quantum optics. This study demonstrated a home-made 852–nm ECDL with variable feedback, using the combined dual narrow-band interference filters (IFs) as the laser longitudinal mode selection element. The combination of narrow-band IFs, mainly for the current commercially available narrow-band IFs with the full width at half maximum (FWHM) of approximately 0.5 nm for 780-895 nm. We designed different narrow-band IFs combinations to achieve a narrower FWHM, and applied them in the ECDL. The combination of the dual narrow-band IFs further reduces the laser linewidth. We measured the laser linewidth using a high-finesse Fabry-Perot cavity with a linewidth of approximately 10 kHz. The laser linewidth is approximately 176 kHz for the Single-IF-ECDL and 96 kHz for the Dual-IF-ECDL with the same feedback. In addition, we have experimentally verified the results of narrower laser linewidth and larger tuning range with increase in the feedback. The developed Dual-IF-ECDL has the capability of narrow linewidth and wavelength tunability and can be applied to precision spectroscopy, cooling and trapping of neutral atoms.

The SIDDHARTA-2 Veto-2 system for X-ray spectroscopy of kaonic atoms at DAΦNE

The Veto-2 is a fundamental component of a multiple-stage veto system for the SIDDHARTA-2 experiment installed at the DAΦNE collider at INFN-LNF in Italy. It was developed to improve the signal-to-background ratio for the challenging measurement of X-ray transitions to the fundamental level in kaonic deuterium. Its purpose is the suppression of hadronic background in the form of Minimum Ionizing Particles by using the topological correlation between signals in the X-ray and Veto-2 detectors. The Veto-2 system consists of a barrel of plastic scintillators read out by Silicon Photomultipliers. The system performed its first successful test run within the apparatus with a helium-4 target in 2022. The efficiency of the Veto-2 was determined and found to be 0.62 ± 0.01. The Veto-2 improved the signal-to-background ratio for the kaonic helium-4 Lα measurement by ∼ 16%, which is crucial due to the low expected X-ray yield of kaonic deuterium.

Revisiting the extraction of charge radii of 40Ca and 208Pb with muonic atom spectroscopy

The extractions of nuclear charge radii from muonic atom spectroscopy for 40Ca and 208Pb are revisited to analyze the model dependencies induced by employing a Fermi-type charge distribution. For that, the charge densities, together with the corresponding muonic transition energies, calculated by the covariant density functional theory are used as a benchmark. The root-mean-square deviation of transition energies is calculated to quantitatively investigate the sensitivities of transition energies to the details of the two-parameter Fermi distribution. It is found that the second and fourth moments of the charge distribution can be extracted accurately from the muonic atom spectroscopy without much model dependencies, whereas the obtained two-parameter Fermi distributions cannot reproduce the details of the benchmarking charge densities and, in particular, its surface-diffuseness parameter cannot be determined accurately with the present experimental uncertainties on the muonic transition energies.

Potentialities of CdZnTe Quasi-Hemispherical Detectors for Hard X-ray Spectroscopy of Kaonic Atoms at the DAΦNE Collider.

Kaonic atom X-ray spectroscopy is a consolidated technique for investigations on the physics of strong kaon-nucleus/nucleon interaction. Several experiments have been conducted regarding the measurement of soft X-ray emission (<20 keV) from light kaonic atoms (hydrogen, deuterium, and helium). Currently, there have been new research activities within the framework of the SIDDHARTA-2 experiment and EXCALIBUR proposal focusing on performing precise and accurate measurements of hard X-rays (>20 keV) from intermediate kaonic atoms (carbon, aluminum, and sulfur). In this context, we investigated cadmium-zinc-telluride (CdZnTe or CZT) detectors, which have recently demonstrated high-resolution capabilities for hard X-ray and gamma-ray detection. A demonstrator prototype based on a new cadmium-zinc-telluride quasi-hemispherical detector and custom digital pulse processing electronics was developed. The detector covered a detection area of 1 cm2 with a single readout channel and interesting room-temperature performance with energy resolution of 4.4% (2.6 keV), 3% (3.7 keV), and 1.4% (9.3 keV) FWHM at 59.5, 122.1, and 662 keV, respectively. The results from X-ray measurements at the DAΦNE collider at the INFN National Laboratories of Frascati (Italy) are also presented with particular attention to the effects and rejection of electromagnetic and hadronic background.

Pulsed CW laser for long-term spectroscopic measurements at high power in deep-UV.

We present a novel technique for in-vacuum cavity-enhanced UV spectroscopy that allows nearly continuous measurements over several days, minimizing mirror degradation caused by high-power UV radiation. Our method relies on pulsing of the cavity's internal power, which increases the UV intensity to maximum only for short periods when the studied atom is within the cavity mode volume while keeping the average power low to prevent mirror degradation. Additionally, this method significantly decreases laser-induced background on charged particle detectors. The described 244 nm laser system is designed for 1S-2S two-photon CW spectroscopy of muonium in the Mu-MASS project. It was tested to provide intracavity powers above 20 W, requiring maintenance only a few times a day. The pulsing technique demonstrates minimal impact on the radiation frequency, with no observed shifts exceeding 15 kHz. Our approach represents a promising new technique for high-precision spectroscopy of atoms in harsh UV environments and demonstrates the feasibility of CW spectroscopy of muonium.

Doppler-free spectroscopy of an atomic beam probed in traveling-wave fields

The authors propose and demonstrate a method for precision spectroscopy of atoms in a beam using two sequential rather than simultaneous laser pulses, thereby overcoming systematic challenges associated with standing-wave beams that plague other methods. Their results show that this method can effectively suppress the first-order Doppler effect and reduce systematic uncertainty.

Muonic atom spectroscopy with microgram target material

Muonic atom spectroscopy–the measurement of the x rays emitted during the formation process of a muonic atom–has a long standing history in probing the shape and size of nuclei. In fact, almost all stable elements have been subject to muonic atom spectroscopy measurements and the absolute charge radii extracted from these measurements typically offer the highest accuracy available. However, so far only targets of at least a few hundred milligram could be used as it required to stop a muon beam directly in the target to form the muonic atom. We have developed a new method relying on repeated transfer reactions taking place inside a 100 bar hydrogen gas cell with an admixture of 0.25% deuterium that allows us to drastically reduce the amount of target material needed while still offering an adequate efficiency. Detailed simulations of the transfer reactions match the measured data, suggesting good understanding of the processes taking place inside the gas mixture. As a proof of principle we demonstrate the method with a measurement of the 2p-1s muonic x rays from a 5 upmu hbox {g} gold target.

Terahertz quantum-cascade lasers for high-resolution absorption spectroscopy of atoms and ions in plasmas

We report on terahertz (THz) quantum-cascade lasers (QCLs) based on GaAs/AlAs heterostructures, which exhibit single-mode emission at 3.360, 3.921, and 4.745 THz. These frequencies are in close correspondence to fine-structure transitions of Al atoms, N+ ions, and O atoms, respectively. Due to the low electrical pump power of these THz QCLs, they can be operated in a mechanical cryocooler in continuous-wave mode, while a sufficient intrinsic tuning range of more than 5 GHz is maintained. The single-mode operation and the intrinsic tuning range of these THz QCLs allow for the application of these lasers as radiation sources for high-resolution absorption spectroscopy to determine the absolute densities of Al atoms, N+ ions, and O atoms in plasmas.

Optical two-dimensional coherent spectroscopy of cold atoms.

We report an experimental demonstration of optical two-dimensional coherent spectroscopy (2DCS) in cold atoms. The experiment integrates a collinear 2DCS setup with a magneto-optical trap (MOT), in which cold rubidium (Rb) atoms are prepared at a temperature of approximately 200 µK and a number density of 1010 cm-3. With a sequence of femtosecond laser pulses, we first obtain one-dimensional second- and fourth-order nonlinear signals and then acquire both one-quantum and zero-quantum 2D spectra of cold Rb atoms. The capability of performing optical 2DCS in cold atoms is an important step toward optical 2DCS study of many-body physics in cold atoms and ultimately in atom arrays and trapped ions. Optical 2DCS in cold atoms/molecules can also be a new avenue to probe chemical reaction dynamics in cold molecules.

Laser spectroscopy of hot atomic vapours: from ’scope to theoretical fit

The spectroscopy of hot atomic vapours is a hot topic. Many of the work-horse techniques of contemporary atomic physics were first demonstrated in hot vapours. Alkali-metal atomic vapours are ideal media for quantum-optics experiments as they combine: a large resonant optical depth; long coherence times; and well-understood atom–atom interactions. These features aid with the simplicity of both the experimental set up and the theoretical framework. The topic attracts much attention as these systems are ideal for studying both fundamental physics and has numerous applications, especially in sensing electromagnetic fields and quantum technology. This tutorial reviews the necessary theory to understand the Doppler broadened absorption spectroscopy of alkali-metal atoms, and explains the data taking and processing necessary to compare theory and experiment. The aim is to provide a gentle introduction to novice scientists starting their studies of the spectroscopy of thermal vapours while also calling attention to the application of these ideas in the contemporary literature. In addition, the work of expert practitioners in the field is highlighted, explaining the relevance of three extensively-used software packages that complement the presentation herein.

Quantum jump spectroscopy of a single neutral atom for precise subwavelength intensity measurements

A single trapped neutral atom is used for precise subwavelength intensity measurements. Quantum jumps from a dark to a bright atomic state are used to boost signal-to-noise and avoid systematic errors.