Spectroscopy Of Atoms Research Articles

Comparison of heating mechanisms of argon helicon plasma in different wave modes with and without blue core

In this work, we investigated the discharge characteristics and heating mechanisms of argon helicon plasma in different wave coupled modes with and without blue core. Spatially resolved spectroscopy and emission intensity of argon atom and ion lines were measured via local optical emission spectroscopy, and electron density was measured experimentally by an RF-compensated Langmuir probe. The relation between the emission intensity and the electron density was obtained and the wavenumbers of helicon and ‘Trivelpiece-Gould’ (TG) waves were calculated by solving the dispersion relation in wave modes. The results show that at least two distinct wave coupled modes appear in argon helicon plasma at increasing RF power, i.e. blue core (or BC) mode with a significant bright core of blue lights and a normal wave (NW) mode without blue core. The emission intensity of atom line 750.5 nm (I ArI750.5nm) is related to the electron density and tends to be saturated in wave coupled modes due to the neutral depletion, while the intensity of ion line 480.6 nm (I ArII480.6nm) is a function of the electron density and temperature, and increases dramatically as the RF power is increased. Theoretical analysis shows that TG waves are strongly damped at the plasma edge in NW and/or BC modes, while helicon waves are the dominant mechanism of power deposition or central heating of electrons in both modes. The formation of BC column mainly depends on the enhanced central electron heating by helicon waves rather than TG waves since the excitation of TG waves would be suppressed in this special anti-resonance region.

Ytterbium optical lattice clock with instability of order 10−18

We have built an ytterbium optical lattice clock with improvements over our previous version. An in-vacuum blackbody radiation (BBR) shield is employed to provide a well characterized BBR environment. The effective temperature felt by the atoms can be determined at an accuracy level of 13 mK, leading to a total BBR frequency shift uncertainty of 9.5 × 10−19. We have also built an ultra-stable optical cavity system to pre-stabilize the clock laser, achieving a flicker frequency instability of ∼3 × 10−16. Rabi spectroscopy of the lattice-trapped atoms can achieve sub-Hertz linewidth spectra. Two ytterbium clocks have been operated in an antisynchronized configuration, with real-time BBR-Stark-shift corrections applied to both of them. By comparing the two clocks, we demonstrate a single-clock instability of 5.4 × 10−18 in 4500 s. This clock will be applied for frequency comparisons to other optical clocks of different atomic species in the future.

Nanoscale 3D Tomography by In-Flight Fluorescence Spectroscopy of Atoms Sputtered by a Focused Ion Beam.

Nanoscale fabrication and characterization techniques critically underpin a vast range of fields, including nanoelectronics and nanobiotechnology. Focused ion beam (FIB) techniques are appealing due to their high spatial resolution and widespread use for processing of nanostructured materials. Here, we introduce FIB-induced fluorescence spectroscopy (FIB-FS) as a nanoscale technique for spectroscopic detection of atoms sputtered by an ion beam. We use semiconductor heterostructures to demonstrate nanoscale lateral and depth resolution and show that it is limited by ion-induced intermixing of nanostructured materials. Sensitivity is demonstrated qualitatively by depth profiling of 3.5, 5, and 8 nm quantum wells and quantitatively by detection of trace-level impurities present at parts-per-million levels. The utility of the FIB-FS technique is demonstrated by characterization of quantum wells and Li-ion batteries. Our work introduces FIB-FS as a high-resolution, high-sensitivity, 3D analysis and tomography technique that combines the versatility of FIB nanofabrication techniques with the power of diffraction-unlimited fluorescence spectroscopy.

The Proton Structure in and out of Muonic Hydrogen

Laser spectroscopy of muonic atoms has been recently used to probe properties of light nuclei with unprecedented precision. We introduce nuclear effects in hydrogen-like atoms, nucleon structure quantities (form factors, structure functions, polarizabilities), and their effects in the Lamb shift and hyperfine splitting (HFS) of muonic hydrogen (μH). Updated theory predictions for the Lamb shift and HFS in μH are presented. We review the challenges of the ongoing effort to measure the ground-state HFS in μH and its impact on our understanding of the nucleon spin structure. To narrow down this search, we present a novel theory prediction obtained by scaling the measured HFS in hydrogen while leveraging radiative corrections. We also summarize recent developments in the spectroscopy of simple atomic and molecular systems and emphasize how they allow for precise determinations of fundamental constants, bound-state QED tests, and New Physics searches.

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex.

Dynamic solution nuclear magnetic resonance (NMR) spectroscopy is the typical method of characterizing the dynamic rearrangements of atoms within the coordination sphere for transition metal polyhydride complexes. Line shape fitting of the dynamic NMR spectra can lead to estimates for the activation parameters of the dynamic rearrangement processes. A combination of dynamic 31P-{1H} NMR spectroscopy of metal-bound phosphorus atoms with dynamic 1H-{31P} NMR spectroscopy of hydride ligands may identify hydride ligand rearrangements that occur in conjunction with a phosphorus atom rearrangement. For molecules that exhibit such a coupled pair of rearrangements, dynamic NMR spectroscopy can be used to test theoretical models for the ligand rearrangements. Dynamic 1H-{31P} NMR spectroscopy and line shape fitting can also identify the presence of an exchange process that moves a specific hydride ligand beyond the metal's inner coordination sphere through a proton exchange with a solvent molecule such as adventitious water. The preparation of a new compound, ReH5(PPh3)2(sec-butyl amine), that exemplifies multiple dynamic rearrangement processes is presented along with line shape fitting of dynamic NMR spectra of the complex. Line shape fitting results can be analyzed by the Eyring equation to estimate the activation parameters for the identified dynamic processes.

Dephasing effect of Rydberg states on trap loss spectroscopy of cold atoms

In this paper, we investigate the asymmetry of trap loss spectra of ultracold atoms during the excitation of Rydberg states. It is shown that the profile of a trap loss spectrum is affected by the density of Rydberg atoms as well as the dephasing rate of Rydberg states. The splitting of a trap loss spectrum is shown at the higher dephasing rates of Rydberg states. A three-level model, where the dephasing rates can be ascribed mainly to a random collision of Rydberg atoms, reasonably explains the experimental results.

Spectroscopy of Alkali Atoms in Solid Matrices of Rare Gases: Experimental Results and Theoretical Analysis

We present an experimental and theoretical investigation of the spectroscopy of dilute alkali atoms in a solid matrix of inert gases at cryogenic temperatures, specifically Rubidium atoms in a solid Argon or Neon matrix, and related aspects of the interaction energies between the alkali atoms and the atoms of the solid matrix. The system considered is relevant for matrix isolation spectroscopy, and it is at the basis of a recently proposed detector of cosmological axions, exploiting magnetic-type transitions between Zeeman sublevels of alkali atoms in a magnetic field, tuned to the axion mass, assumed in the meV range. Axions are one of the supposed constituents of the dark matter (DM) of the Universe. This kind of spectroscopy could be also relevant for the experimental search of new physics beyond the Standard Model, in particular the search of violations of time-reversal or parity-charge-conjugation (CP) symmetry. In order to efficiently resolve the axion-induced transition in alkali-doped solid matrices, it is necessary to reduce as much as possible the spectral linewidth of the electronic transitions involved. The theoretical investigation presented in this paper aims to estimate the order of magnitude of the inhomogeneous contribution to the linewidth due to the alkali–matrix interactions (Coulomb/exchange and dispersion), and to compare the theoretical results with our experimental measurements of spectra of dilute Rubidium atoms in Argon and Neon solid matrix. The comparison of the expected or measured spectral linewidths will be important for selecting the most appropriate combination of alkali atoms and matrix inert elements to be used in the proposed axion detection scheme. It is finally suggested that dilute Lithium atoms diffused in a cold parahydrogen solid matrix could be, overall, a good system upon which the proposed detector could be based.

Spectroscopy of He atom encapsulated in C60 cage: low lying magnetic dipolar (M1) and magnetic quadrupolar (M2) transitions

The spectroscopic properties of magnetic dipolar and quadrupolar transitions (M1 and M2) of He atom encapsulated under neutral and charged C60 fullerene cage have been estimated here to understand the effect of cage confinement on the ground state energy ( E), ionization potential (IP), excitation energies (Δ E), and transition probabilities (TPs) of the low lying transitions 1s2:1Se → 1s ns:3S[Formula: see text] and 1s2:1Se → 1s np:3P[Formula: see text] ( n = 2, 3, 4, 5). The methodology adopted is the time-dependent coupled Hartree–Fock theory within a variational scheme, which incorporates partial correlation effects. The effect of encapsulation has been introduced through an effective potential in the one particle potential part due to the fullerene cage. Interesting pattern of the relevant properties of the confined He atom has been observed depending upon overall charge of the fullerene cage.

Frequency-stabilized Faraday laser with 10−14 short-term instability for atomic clocks

In this Letter, stabilizing a Faraday laser frequency to the atomic transition is proposed and experimentally demonstrated, where the Faraday laser can work at single- or dual-frequency modes. High-resolution spectroscopy of a cesium atom induced by a Faraday laser is obtained. By stabilizing a Faraday laser with atomic spectroscopy, the frequency fluctuations of the Faraday laser are suppressed without the need of a high-cost Pound–Drever–Hall system. The fractional frequency Allan deviation of the residual error signal is 3 × 10−14/τ at the single-frequency mode. While at the dual-frequency mode, the linewidth of the beat-note spectra between the two modes of the Faraday laser after locking is narrowed to be 85 Hz, which is an order of magnitude better than the free-running linewidth. It can be used for microwave atomic clocks and may have the potential to be used in the application of optical microwave generation when the performance is further improved.

Laser-frequency stabilization with differential single-beam saturated absorption spectroscopy of 4He atoms.

Differential single-beam saturated-absorption spectroscopy (DSSAS) is proposed to stabilize lasing frequency and suppress Doppler-broadened background and common-mode optical noise. The spectral first-derivative demodulated signal of metastable He4 atoms is used as an error signal to stabilize a fiber laser around 1083 nm. Experimental results show that, compared with existing non-DSSAS frequency stabilization, DSSAS stabilization produces better stability and lower fluctuations, especially for frequency-noise-corrupted lasers. In DSSAS stabilization, for data acquired over 7000 s, the root mean square frequency fluctuation of the fiber laser is 16.4 kHz, and the frequency stability described by the modified Allan deviation is 4.1 × 10-12 at 100 s. Even for a defective laser with poor frequency stability, the proposed scheme demonstrates experimentally high capability of noise suppression and reduces the frequency fluctuations by two orders of magnitude. Given its simplicity and compact design, frequency stabilization by DSSAS is promising for quantum-sensor applications, such as atomic magnetometers, atomic gyroscopes, and atomic clocks.

A search for atomic parity violation in muonic atoms using a high-intensity pulsed muon beam at J-PARC

An exotic atom consisting of a negative muon and a nucleus is a muonic atom. Atomic parity violation in muonic atoms provides a unique opportunity to determine the Weinberg angle and search for physics beyond the standard model at the low energy scale. We have proposed a new experiment to perform X-ray spectroscopy of muonic atoms using a high-intensity pulsed muon beam at J-PARC. A scintillator-based calorimeter and a lowdensity gaseous target were developed for the experiment. As a feasibility study, we measured the yield of muon atoms and searched for muonic atom’s metastability using low-density methane gas. An overview of the experiment and the test experiment results are presented.

X ray spectroscopy on 𝚵− atoms (J-PARC E03, E07 and future)

X-ray spectroscopy of hadronic atoms is a powerful method to study strong interaction between hadrons and nuclei. At J-PARC, we have conducted two experiments, J-PARC E07 and E03, for hadronic atoms with a doubly strange hyperon, Ξ−, aiming at the world-first detection of their X-rays. The first measurement is performed as a byproduct of J-PARC E07 experiment with the hybrid emulsion technique. The second one, J-PARC E03, is a dedicated experiment for detection of Ξ− Fe atom X rays. The preliminary results and the present status of E07 and E03 are shown in this article. Future prospects of Ξ−-atomic X-ray spectroscopy are also discussed. A new measurement has been proposed for detecting Ξ− C atom X rays, where a novel Ξ− tracking method will be applied to realize an improved signal to noise ratio.

Main Features of the SIDDHARTA-2 Apparatus for Kaonic Deuterium X-Ray Measurements

The low-energy, non-perturbative regime of QCD can be studied directly by X-ray spectroscopy of light kaonic atoms. The SIDDHARTA-2 experiment, located at the DAΦNE collider, aims to measure the 2p → 1s transition in kaonic deuterium for the first time to extract the antikaon-nucleon scattering lengths. This measurement is impeded, inter alia, by the low K−d X-ray yield. Hence, several updates have been implemented on the apparatus to increase the signal-to-background ratio, which are discussed in detail in this paper: a lightweight gas target cell, novel Silicon Drift Detectors for the X-ray detection with excellent performance, and a veto system for active background suppression. The experiment has undergone a first preparatory run during DAΦNE’s commissioning phase in 2021, concluding with a successful kaonic helium measurement.

Transient electromagnetically induced transparency spectroscopy of 87Rb atoms in buffer gas

We study the transient response dynamics of 87Rb atomic vapor buffered in 8 torr Ne gas through an electromagnetically induced transparency configured in Λ-scheme. Experimentally, the temporal transmission spectra versus probe detuning by switching on and off the coupling one show complex structures. The transmitted probe light intensity drops to a minimum value when the coupling light turns off, showing a strong absorption. Even at the moment of turning on the coupling light at a subsequent delayed time, the atomic medium shows a fast transient response. To account for the transient switching feature, in the time-dependent optical Bloch equation, we must take the transverse relaxation dephasing process of atomic vapor into account, as well as the fluorescence relaxation along with the optical absorption. This work supplies a technique to quantify the transverse relaxation time scale and to sensitively monitor its variation along the environment by observing the transient dynamics of coherent medium, which is helpful in characterizing the coherent feature of the atomic medium.

High-resolution spectroscopy of neutral Yb atoms in a solid Ne matrix

We present an experimental and theoretical study of the absorption and emission spectra of Yb atoms in a solid Ne matrix at a resolution of 0.025 nm. Five absorption bands were identified as due to transitions from the $4{f}^{14}5{d}^{0}6{s}^{2}{\phantom{\rule{4pt}{0ex}}}^{1}{S}_{0}$ ground-state configuration to $4{f}^{14}5{d}^{0}6s6p$ and $4{f}^{13}5{d}^{1}6{s}^{2}$ configurations. The two lowest-energy bands were assigned to outer-shell transitions to $6s6p{\phantom{\rule{4pt}{0ex}}}^{3}{P}_{1}$ and ${}^{1}{P}_{1}$ atomic states and displayed the structure of a broad doublet and an asymmetric triplet, respectively. The remaining three higher-frequency bands were assigned to inner-shell transitions to distinct $J=1$ states arising from the $4{f}^{13}5{d}^{1}6{s}^{2}$ configuration and were highly structured with narrow linewidths. A classical simulation was performed to identify the stability and symmetry of possible trapping sites in the Ne crystal. It showed that the overarching $1+2$ structure of the high-frequency bands could be predominantly ascribed to crystal-field splitting in the axial field of a 10-atom vacancy of ${C}_{4v}$ symmetry. Their prominent substructures were shown to be manifestations of phonon sidebands associated with the zero-phonon lines on each crystal-field state. Unprecedented for a metal--rare-gas system, resolution of individual phonon states on an allowed electronic transition was possible under excitation spectroscopy which reflects the semiquantum nature of solid Ne. In contrast to the absorption spectra, emission spectra produced by steady-state excitation into the ${}^{1}{P}_{1}$ absorption band consisted of simple, unstructured fluorescence bands.

Microwave two-photon spectroscopy of cesium Rydberg atoms

We present a two-photon microwave spectra of cesium Rydberg atoms in the room-temperature vapor cell. The three-level atom including a ground state 6S1/2 (F = 4), an excited state 6P3/2 (F′ = 5) and Rydberg state consists of Rydberg electromagnetically induced transparency (Rydberg-EIT), that is employed to detect the microwave two-photon spectra. The microwave field with frequency ν DD = 11.42865 GHz couples the transition of Rydberg energy level |68D5/2〉 → |69D5/2〉, measured two-photon spectra display a rich of information including the microwave ac Stark shifts and two-photon Autler-Townes (AT) splitting. In the strong microwave field, the two-photon spectroscopy shows the state mixture between |68D5/2〉 and |68D3/2〉 Stark lines. The microwave two-photon spectra of the |69S1/2〉 → |70S1/2〉 transition coupled with frequency ν SS = 11.73503 GHz are also presented. The Floquet theory is employed to simulate the two-photon microwave spectra, showing the good agreement with the measurements. The work suggests the new method that may be used to investigate the multi-photon field-atom interaction and as an atom-based technique for precision field measurements.

Silicon Drift Detectors’ Spectroscopic Response during the SIDDHARTA-2 Kaonic Helium Run at the DAΦNE Collider

A large-area silicon drift detectors (SDDs) system has been developed by the SIDDHARTA-2 collaboration for high precision light kaonic atom X-ray spectroscopy at the DAΦNE collider of Istituto Nazionale di Fisica Nucleare—Laboratori Nazionali di Frascati. The SDDs’ geometry and electric field configuration, combined with their read-out electronics, make these devices suitable for performing high precision light kaonic atom spectroscopy measurements in the background of the DAΦNE collider. This work presents the spectroscopic response of the SDDs system during the first exotic atoms run of SIDDHARTA-2 with kaonic helium, a preliminary to the kaonic deuterium data taking campaign. The SIDDHARTA-2 spectroscopic system has good energy resolution and a 2 μs timing window which rejects the asynchronous events, scaling the background by a factor of 10−5. The results obtained for the first exotic atoms run of SIDDHARTA-2 prove this system to be ready to perform the challenging kaonic deuterium measurement.

Continuous operation of a bicolor thulium optical lattice clock

We discuss the extension of a recently proposed method based on continuous spectroscopy of 88Sr atoms trapped in a moving optical lattice [Appl. Phys. Express, 14, 072 006 (2021)] to the operation of bicolor thulium optical clocks. Simultaneous interrogation of two clock transitions at 1.14 μm and build-up of a synthetic frequency provides a straightforward way to significantly suppress the first-order Doppler shift and cancel out the second-order Zeeman shift, the latter being one of the major sources of uncertainty in the originally proposed 88Sr setup. In our configuration, the total systematic frequency shift is 4 × 10−16 and instability is at or lower than 10−18 after 1 h of integration.

Compact magneto-optical trap of thulium atoms for a transportable optical clock.

We have developed a compact vacuum system for laser cooling and spectroscopy of neutral thulium atoms. Compactness is achieved by obviating a classical Zeeman slower section and placing an atomic oven close to a magneto-optical trap (MOT), specifically at the distance of 11 cm. In this configuration, we significantly gained in solid angle of an atomic beam, which is affected by MOT laser beams, and reached 1 million atoms loaded directly in the MOT with only 15 mW of MOT cooling beams net power. By exploiting Zeeman-like deceleration of atoms with an additional laser beam and tailoring the MOT magnetic field gradient with a small magnetic coil, we demonstrated trapping of up to 13 million atoms. These results show great perspective of the developed setup for realizing a compact high-performance optical atomic clock based on thulium atoms.

Double‐Twisted Spectroscopy with Delocalized Atoms

AbstractInteraction of atoms with twisted light is the subject of intense experimental and theoretical investigation. In almost all studies, the atom is viewed as a localized probe of the twisted light field. However, as argued in this paper, conceptually novel effects will arise if light‐atom interaction is studied in the double‐twisted regime with delocalized atoms, that is, either via twisted light absorption by atom vortex beam, or via two‐twisted‐photon spectroscopy of atoms in a non‐vortex but delocalized state. Even for monochromatic twisted photons and for an infinitely narrow line, absorption will occur over a finite range of detuning. Inside this range, a rapidly varying absorption probability is predicted, revealing interference fringes induced by two distinct paths leading to the same final state. The number, location, height, and contrast of these fringes can give additional information on the excitation process which would not be accessible in usual spectroscopic settings. Visibility of the predicted effects will be enhanced at the future Gamma factory thanks to the large momenta of ions.