Atomic Spectra Research Articles

Frequency measurement of 6s6p 3P0,2−6s7s 3S1 transitions in ultracold 171Yb atoms referenced to local optical clock

We experimentally determine the absolute frequencies and hyperfine splittings of the 6s6p3P0,2 − 6s7s3S1 transitions of ultracold 171Yb atoms in an optical lattice. A frequency comb referenced to an ultrastable optical cavity is used to measure the electric-dipole transition frequencies. With the normalized shelving detection technique, about 12 MHz and 10 MHz linewidth of atomic spectra are obtained, respectively, which is some greater than the natural linewidth of 1.5 MHz and 5.9 MHz and is limited by the broadening from the probe and lattice light. By reference to our 171Yb 6 s2 1S0 − 6s6p3P0 clock, the absolute frequencies are found to be 461861338.03 (0.21) MHz and 461871596.07 (0.31) MHz for the 6s6p3P0 − 6s7s3S1 (F = 1/2 and F = 3/2) transitions, which are more accurate than the previous measurement by one order of magnitude. For the 6s6p3P2 (F = 3/2 and F = 5/2) − 6s7s3S1 (F = 1/2 and F = 3/2) transitions, the measured frequencies are 389257019.71 (0.65) MHz, 389267277.10 (0.37) MHz and 389260569.95 (0.89) MHz, respectively, which are the first measurements to our knowledge. Furthermore, the hyperfine constants for the 6s6p3P2 and 6s7s3S1 states are determined to be 2682.86(0.38) MHz and 6838.69(0.25) MHz, both of which agree well with other recent experimental results.

Wavefunction Collapse Broadens Molecular Spectrum

Spectral lines in the optical spectra of atoms, molecules, and other quantum systems are characterized by a range of frequencies ω or a range of wavelengths λ=2πc/ω, where c is the speed of light. Such a frequency or wavelength range is called the width of the spectral lines (linewidth). It is influenced by many specific factors. Thermal motion of the molecules results in broadening of the lines as a result of the Doppler effect (thermal broadening) and by their collisions (pressure broadening). The electric fields of neighboring molecules lead to Stark broadening. The linewidth to be considered here is the so-called parametric broadening (PB) of spectral lines in the optical spectrum. PB can be considered the fundamental type of broadening of the electronic vibrational–rotational (rovibronic) transitions in a molecule, which is the direct manifestation of the basic concept of the collapse of a wavefunction that is postulated by the Copenhagen interpretation of quantum mechanics. Thus, that concept appears to be not only valid but is also useful for predicting physically observable phenomena.

Chiral symmetry restoration at high matter density observed in pionic atoms

According to quantum chromodynamics, vacuum is not an empty space, because it is filled with quark–antiquark pairs. The pair has the same quantum numbers as the vacuum and forms a condensate because the strong interaction of the quantum chromodynamics is too strong to leave the vacuum empty. This quark–antiquark condensation, the chiral condensate, breaks the chiral symmetry of the vacuum. The expectation value of the chiral condensate is an order parameter of the chiral symmetry, which is expected to decrease at high temperatures or high matter densities where the chiral symmetry is partially restored. Head-on collisions of nuclei at ultra-relativistic energies have explored the high-temperature regime, but experiments at high densities are rare. Here we measure the spectrum of pionic 121Sn atoms and study the interaction between the pion and the nucleus. We find that the expectation value of the chiral condensate is reduced at finite density compared to the value in vacuum. The reduction is linearly extrapolated to the nuclear saturation density and indicates that the chiral symmetry is partially restored due to the extremely high density of the nucleus. In quantum chromodynamics, the condensation of quark–antiquark pairs breaks the chiral symmetry of vacuum. Experiments with pionic tin atoms demonstrate that the symmetry is partially restored at high densities.

Investigating the effect of volatility on the hygroscopicities of acetate nanoparticle aerosols by surface plasmon resonance microscopy

Under high relative humidity (RH) conditions, the release of volatile components (such as acetate) has a significant impact on the aerosol hygroscopicity. In this work, one surface plasmon resonance microscopy (SPRM) measurement system was introduced to determine the hygroscopic growth factors (GFs) of three acetate aerosols separately or mixed with glucose at different RHs. For Ca(CH3COO)2 or Mg(CH3COO)2 aerosols, the hygroscopic growth trend of each time was lower than that of the previous time in three cyclic humidification from 70% RH to 90% RH, which may be due to the volatility of acetic acid leading to the formation of insoluble hydroxide (Ca(OH)2 or Mg(OH)2) under high RH conditions. Then the third calculated GF (using the Zdanovskii-Stokes-Robinson method) for Ca(CH3COO)2 or Mg(CH3COO)2 in bicomponent aerosols with 1:1 mass ratio were 3.20% or 5.33% lower than that of the first calculated GF at 90% RH. The calculated results also showed that the hygroscopicity change of bicomponent aerosol was negatively correlated with glucose content, especially when the mass ratio of Mg(CH3COO)2 to glucose was 1:2, the GF at 90% RH only decreased by 4.67% after three cyclic humidification. Inductively coupled plasma atomic emission spectrum (ICP-AES) based measurements also indicated that the changes of Mg2+concentration in bicomponent was lower than that of the single-component. The results of this study reveal thatduring the efflorescence transitions of atmospheric nanoparticles, the organic acids diffusion rate may be inhibited by the coating effect of neutral organic components, and the particles aging cycle will be prolonged.

Discussion on the Problems of Bohr’s Hydrogen Atom Theory in Basic Theory

According to the charge momentum and charge kinetic energy, it is proved that the key problem of the basic theory of Bohr hydrogen atom is that equation does not hold. For the same electron of the hydrogen atom, the left side of the equation is the mechanical kinetic energy, the right side of the equation is the charge energy, the fundamental properties and the concept of energy are split. Based on experiments, this paper analyzes and calculates the combined energy of hydrogen, lithium and oxygen atoms, hydrogen atom radius and the ground state energy of hydrogen atom are obtained. This ground state energy is basically consistent with the Balmer system of hydrogen atomic spectrum ; Electron around the nuclear velocity . hydrogen atom radius is calculated by using energy , which verifies the correctness of charge momentum and charge kinetic energy and their experimental basis. The ground state energy atom and radius of Bohr hydrogen is derived under the condition that the basic theory has problems and the theoretical formula is set to , which has no experimental basis. The fundamental problem of quantum mechanics is that the theoretical formula of photoelectric effect is not correct, which is demonstrated in this paper. The relationship between the structure of hydrogen atom and the evolution of the universe is also discussed.

Potential energy surfaces for electron dynamics from a model of localized Gaussian wave packets with valence-bond spin-coupling: High-harmonic generation spectra from H and He atoms

Potential energy surfaces of electron dynamics (ePES) are constructed from a model of localized electron wave packets (eWP) with non-orthogonal valence-bond (VB) spin coupling and applied to quantum dynamics simulations of high harmonic generation (HHG) spectra of hydrogen and helium atoms induced by intense laser pulses. The dynamics of the single electron on the ePES is calculated by numerically solving the time-dependent Schrödinger equation. The results reasonably reproduce previous studies. The dynamics of the electron wave function, dipole moment and dipole acceleration were analyzed by comparing one- and two-dimensional calculations. It was found that the main part of the wave function remains within a few Bohrs of the nuclear position, while the part of the wave function that is several orders of magnitude smaller in probability density, which escapes the laser-induced potential barrier by quantum tunneling effect, mainly contributes to the HHG.

New Determinations of the Surface Abundances of HD 1280

New abundances for several chemical elements are measured for HD 1280 using updated atomic data and spectrum synthesis. The abundances of calcium and scandium are solar whereas strontium is mildly overabundant. The abundances of helium, magnesium, titanium, chromium, manganese, iron and barium are in good agreement with a former abundance analysis. This reinforces the status of HD 1280 as a normal rapidly rotating A star with essentially normal abundances of elements lighter than iron and mild overabundances of heavier elements which may actually have been present in the environment where the star was born.

New Determinations of the Surface Abundances of HD 1909: Paper II: From Calcium to Mercury

New abundances for the elements calcium to mercury are measured for the brightest member of the spectroscopic binary HD 1909 using updated atomic data and spectrum synthesis. Manganese is overabundant by a unusually high factor (80 ⊙). While strontium is underabundant, yttrium and zirconium are very overabundant by factors of 250 and 500 times the solar abundances. Barium is overabundant by a factor of 20. The strongest lines of the twice ionized lanthanides Pr iii and Nd iii are not present which suggests the abundances of these two elements are solar or less. The Hg ii line at 3983.93 Å is unusually strong and reproduced by a mercury overabundance of a factor of 500,000 times the solar mercury abundance.

Lifetime of excitations in atomic and molecular Bose-Einstein condensates

Recent experimental progress has produced Molecular Superfluids (MSF) in thermal equilibrium; this opens the door to a new class of experiments investigating the associated thermodynamic and dynamical responses. We review the theoretical picture of the phase diagram and quasiparticle spectrum in the Atomic Superfluid (ASF) and MSF phases. We further compute the parametric dependence of the quasiparticle lifetimes at one-loop order. In the MSF phase, the $U(1)$ particle number symmetry breaks to $\mathbb{Z}_2$ and the spectrum exhibits a gapless Goldstone mode in addition to a gapped $\mathbb{Z}_2$-protected atom-like mode. In the ASF phase, the $U(1)$ symmetry breaks completely, leaving behind a Goldstone mode and an unprotected gapped mode. In both phases, the Goldstone mode decays with a rate given by the celebrated Belyaev result, as in a single component condensate. In the MSF phase, the gapped mode is sharp up to a critical Cherenkov momentum beyond which it emits phonons. In the ASF phase, the gapped mode decays with a constant rate even at small momenta. These decay rates govern the spectral response in microtrap tunneling experiments and lead to sharp features in the transmission spectrum of atoms fired through molecular clouds.

Synthesis and Characterization of CaFe1.925Gd0.025Sm0.05O4/PEG Core–Shell Nanoparticles for Diverse Applications

The core–shell structure has been studied by coating polyethylene glycol (PEG) on rare-earth-doped calcium ferrite nanoparticles (RCFNPs). RCFNPs are successfully synthesized in the formula CaFe1.925Gd0.025Sm0.05O4 by the citrate nitrate auto-combustion method. The XRD pattern of PEG-coated RCFNPs observed two peaks at 19.3° and 23.6° confirming the existence of PEG, while the other peaks are attributed to the orthorhombic structure formation. The obtained samples exhibit an orthorhombic single-phase structure with an average crystallite size in the range of 18–20 nm. The elemental analysis is performed using EDAX and XPS. The doublet spectrum of Fe atoms corresponds to the valence states Fe 2P1/2 and Fe 2P3/2. High-resolution transmission electron microscopy (HRTEM) revealed a well-designed hexagonal core/shell structure represented as a unique hexagonal PEG shell coating the synthesized RCFNPs. The magnetic hysteresis loops have been recorded using VSM. The coupling between the unpaired electrons of Fe+3 and Sm+3 ions via the p orbitals of the O−2 ions leads to the antiferromagnetic alignment. The smaller values of the switching-field distribution (SFD) and higher coercivity of the prepared samples are most appropriate for ultra-high-density recording performance. The behavior of dielectric parameters is explained on the basis of the interfacial polarization and the Maxwell–Wagner polarization models. Diffuse reflectance spectroscopy (DRS) is used to study the performance of electromagnetic reflection and estimate the optical band gaps of the samples. The obtained data shows that the coating has an important role in enhancing the reflection by up to 50%.

Simultaneous denoising and resolution enhancement of seismic data based on elastic convolution dictionary learning

Enhancing seismic resolution is a key component in seismic data processing, which plays a valuable role in raising the prospecting accuracy of oil reservoirs. However, in noisy situations, existing resolution enhancement methods are difficult to yield satisfactory processing outcomes for reservoir characterization. To solve this problem, we develop a new approach for simultaneous denoising and resolution enhancement of seismic data based on convolution dictionary learning. First, an elastic convolution dictionary learning algorithm is presented to efficiently learn a convolution dictionary with stronger representation capability from the noisy data to be processed. Specifically, the algorithm introduces the elastic L1/2 norm as a sparsity constraint and employs a steepest gradient descent strategy to efficiently solve the frequency-domain linear system with substantial computational cost in a half-quadratic splitting framework. Then, based on the learned convolution dictionary, a weighted convolutional sparse representation paradigm is designed to encode the noisy data to acquire an optimal sparse approximation of the effective signal. Subsequently, a high-resolution dictionary with a broadband spectrum is constructed by the proposed parameter scaling strategy and matched filtering technique on the basis of atomic spectrum modeling. Finally, the optimal sparse approximation of the effective signal and the constructed high-resolution dictionary are used for data reconstruction to obtain the seismic signal with high resolution and high signal-to-noise ratio. Synthetic and field dataset examples are executed to check the effectiveness and reliability of the developed method. The results indicate that this method has a more competitive performance in seismic applications compared with the conventional deconvolution and spectral whitening methods.

New Determinations of the Surface Abundances of HD 1909: Paper I: The Light Elements (from Helium to Sulfur)

New abundances for the elements helium to sulfur are derived for the brightest member of the spectroscopic binary HD 1909 using updated atomic data and spectrum synthesis. The majority of these elements are underabundant, the depletion factors appear in parenthesis: helium (0.02 times the solar helium abundance), carbon and oxygen (0.40 ⊙), neon (0.15 ⊙), magnesium (0.45 ⊙), aluminum (0.02 ⊙). silicon (0.50 ⊙) and sulfur (0.35 ⊙). In contrast, phosphorus is overabundant by a factor of 12.5 ⊙ and the silicon–phosphorus–sulfur triad is inverted. The lines of the companion are redshifted by about +122.5 km s−1 with respect to the B9 Hg star in the spectrum analyzed here.

Machine learning in analytical spectroscopy for nuclear diagnostics [Invited

Analytical spectroscopy methods have shown many possible uses for nuclear material diagnostics and measurements in recent studies. In particular, the application potential for various atomic spectroscopy techniques is uniquely diverse and generates interest across a wide range of nuclear science areas. Over the last decade, techniques such as laser-induced breakdown spectroscopy, Raman spectroscopy, and x-ray fluorescence spectroscopy have yielded considerable improvements in the diagnostic analysis of nuclear materials, especially with machine learning implementations. These techniques have been applied for analytical solutions to problems concerning nuclear forensics, nuclear fuel manufacturing, nuclear fuel quality control, and general diagnostic analysis of nuclear materials. The data yielded from atomic spectroscopy methods provide innovative solutions to problems surrounding the characterization of nuclear materials, particularly for compounds with complex chemistry. Implementing these optical spectroscopy techniques can provide comprehensive new insights into the chemical analysis of nuclear materials. In particular, recent advances coupling machine learning methods to the processing of atomic emission spectra have yielded novel, robust solutions for nuclear material characterization. This review paper will provide a summation of several of these recent advances and will discuss key experimental studies that have advanced the use of analytical atomic spectroscopy techniques as active tools for nuclear diagnostic measurements.

Diagnostics of laser-induced plasma on carbon-based polymer material using atomic and molecular emission spectra

Time-integrated optical emission analysis of laser-induced plasma on Teflon is presented. Plasma was induced under atmospheric pressure air using transversely excited atmospheric CO2 laser pulses. Teflon is a C-based polymer that is, among other things, interesting as a substrate for laser-induced breakdown spectroscopy analysis of liquid samples. This study aimed to determine the optimal experimental conditions for obtaining neutral and ionized C spectral lines and C2 and CN molecular band emission suitable for spectrochemical purposes. Evaluation of plasma parameters was done using several spectroscopic techniques. Stark profiles of appropriate C ionic lines were used to determine electron number density. The ratio of the integral intensity of ionic-to-atomic C spectral lines was used to determine the ionization temperature. A spectral emission of C2 Swan and CN violet bands system was used to determine the temperature of the colder, peripheral parts of plasma. We critically analyzed the use of molecular emission bands as a tool for plasma diagnostics and suggested methods for possible improvements.

A wide-band, high-resolution vacuum flat crystal spectrometer for LEAF facility

A wide-band, high-resolution vacuum flat-crystal spectrometer was developed for analyzing the x-rays spectra of hollow atoms. The spectrometer was designed to cover an energy dynamic range of 0.6 to 16 keV by combining different flat crystals and an x-ray CCD detector mounted on a twistable bellows that could modulate the Bragg angles ranging from 25° to 50°.The performance of the spectrometer was evaluated in energy range of 3–12 keV by measuring the K and L x-rays generated by 10–30 keV electron beam collisions with solid titanium, silver and gold targets, respectively. The typical resolving power of the spectrometer is estimated to be around 103, with a single exposure measurement range of 144–1411 eV and corresponding energy resolution of 3.5–33.2 eV. This spectrometer could be utilized to investigate the fine hyper-satellite line structure of hollow atoms with 10 ≤ Z ≤ 26.

A High-Efficiency Fiber-Coupled Rydberg-Atom Integrated Probe and Its Imaging Applications

Atomic sensing and electric field measurements based on the use of the all-optical electromagnetic induction transparency (EIT) spectrum of Rydberg atoms have attracted great interest due to the advantages of self-calibration, Le Système International d'unités traceability, and a broadband spectrum. At the same time, this methodology also promotes the development of atomic sensor technology. We present a novel high-efficiency Rydberg-atom radio-frequency (RF) electric (E) field integrated probe (Rydberg Field Probe or RFP). The high-efficiency RFP consists of a 10 mm cubic 133Cs vapor cell, a dichroic mirror, three collimating lenses, and three fibers. This system can be used to independently control two counterpropagating lasers passing through a vapor cell, easing the design effort. In addition, the overall system efficiency can reach a value of 40.4%, reducing the EIT power broadening doe conventional RFPs. Based on the designed high-efficiency RFP, near-field electric field measurement and imaging of a C-band horn antenna at 4.48 GHz are performed by using the resonant RF field of the 133Cs atomic Rydberg state at room temperature with a spatial resolution of λ/6. These results promote the development of atomic sensing technology and show great application potential for the measurement of measuring high-resolution radio frequency electric fields and arrays of RFPs.

Synthesis and Characterization Complexes of Cobalt(II), Nickel(II), Copper(II) and Palladium with [N'-{2-(4-isobutyl-phenyl)-propionyl} pyridine-4-carbohydrazide

This research concern with the metal complexes of the ligand [N'-{2-(4-isobutyl-phenyl)-propionyl}pyridine-4-carbohydrazide] with Co(II), Ni(II) , Cu(II) and Pd(II) have been synthesized and characterized by atomic absorption , infrared, electronic spectra, molar conductivity and magnetic moment measurements. On the basis of the data obtained from the above measurements, the ligand act as a neutral bidentate and the octahedral structures are proposed for the Co(II), Ni(II) and Cu(II) while the square planer structures are assigned to Pd(II) complexes.

Radiation influence on the plasma atomic kinetics and spectra in experiments on radiative shock waves

Radiative shocks waves are among of the most interesting astrophysical phenomena and due to their relevance, many laboratory experiments, using high-power lasers, have been performed to achieve a better understanding of them. The radiation emitted by the shock front can heat and ionize the pre-shock medium leading to the formation of radiative precursors, which are relevant in these phenomena since they absorb part of the radiation emitted by the shock front and becomes a strong source of radiation emission. The plasma in the precursor can be considered as a photoionized plasma in which the external radiation field plays a dominant role in the atomic kinetics behavior. A numerical study of the influence of the radiation field on the ion populations, radiative properties and atomic spectra of radiative precursors in radiative shocks generated in two laboratory experiments is presented. For the numerical simulations, three types of collisional-radiative models have been used. In the first one, the radiation induced processes are not included. In the second type, the radiative atomic processes induced by plasma self-absorption are considered. Finally, the radiative processes induced by both the external radiation field and the plasma self-absorption are included. The results obtained show the noticeable influence of the radiation field on the plasma properties analyzed.

Effect of cavity leakage on time-dependent spectrum of two atoms Tavis-Cummings model

We study the atomic emission spectrum and cavity field spectrum of dipole–dipole coupled two atoms interacting with a single-mode radiation field in a non-ideal cavity. We solved the quantum master equation by a method that combined analytical analysis and numerical solution. The explicit expression of spectral peak position and numerical results of spectral structure are given for the atoms in entangled state and the field in vacuum initially. The results shown that the decay rate of cavity field has obvious influence on the intensity of spectra but a little effect on the spectral structure. The cavity dissipation makes also the measurement time an important factor in measuring spectral structure.

Comparison of light capturing approaches in Laser-Induced Breakdown Spectroscopy (LIBS) for multichannel spectrometers

LIBS technique requires the spectroscopic analysis of the light emitted by a laser-induced plasma plume. One challenge of the different approaches to capture the plasma light emission is the significant shot-to-shot variations of the plume inhomogeneities, position, and morphology. This is even more challenging when multichannel CCD spectrometers are used, because the light should be homogeneously divided among multiple capturing optical fibers (typically up to 8 fibers) with stable spectral efficiency for all channels. Otherwise, any further analysis of the atomic emission spectra involving multiple channels, such as line intensity ratios, Boltzmann plots, or calibration-free LIBS, could be compromised by the morphology-dependent spectral artifacts induced by the collection optics. In this work, we assess the performance of several collection optics in terms of overall capturing efficiency and channel-to-channel variations due to changes in plasma morphology. Results clearly show that this could be an issue even with the approaches with the best spatial homogenization, including optical fibers and Köhler optics.