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Measurements of the L-shell X-ray emission of fluorine-like europium ions (Eu54+) were made under controlled laboratory conditions on the EBIT-I electron beam ion trap at Livermore using an X-ray calorimeter, extending such measurements to the middle of the rare earth elements. Comparing the calorimeter spectra with atomic data from the flexible atomic code, we have identified and analyzed several prominent n = 3 → n = 2 transitions, including one two-electron, one-photon core changing transition and one electric quadrupole transition. We find that the measured energies are typically up to several eV higher than predicted. [ABSTRACT FROM AUTHOR]

The luminescence excitation spectra of the D1 resonance line of atoms K, Rb, and Cs in gas mixtures with CF4 are found to contain satellite transitions, which correspond to the transition of an atom to the states (n – 1)d2D3/2,5/2 and (n + 1)s2S1/2, where n = 4, 5, and 6 for K, Rb, and Cs, respectively, with the simultaneous excitation of CF4 molecule vibrations at the IR active mode frequency ν3 with a quantum energy of 1283 cm–1. These satellite transitions are A(ns2S1/2) + CF4(ν3 = 0) + hν → A((n – 1)d2D3/2,5/2) + CF4(ν3 = 1) and A(ns2S1/2) + CF4(ν3 = 0) + hν → A((n + 1)s2S1/2) + CF4(ν3 = 1), where A = K, Rb, and Cs. The appearance of an optical coupling between the upper and lower states of these asymptotically (at → ∞) forbidden transitions is shown to be caused by the interaction of the dipole moment of the ν3 = 1 ↔ ν3 = 0 vibrational transition in the CF4 molecule with the dipole moments of the electronic transitions np2P1/2,3/2 ↔ (n – 1)d2D3/2,5/2 and np2P1/2,3/2 ↔ (n + 1)s2S1/2 in an alkali metal atom; as a result of this interaction, the upper state of the satellite transition acquires admixtures of the A(np2P1/2,3/2)CF4(ν3 = 0) resonance states. [ABSTRACT FROM AUTHOR]

The luminescence excitation spectra of the D1 resonance line of atoms K, Rb, and Cs in gas mixtures with CF4 are found to contain satellite transitions, which correspond to the transition of an atom to the states (n – 1)d2D3/2,5/2 and (n + 1)s2S1/2, where n = 4, 5, and 6 for K, Rb, and Cs, respectively, with the simultaneous excitation of CF4 molecule vibrations at the IR active mode frequency ν3 with a quantum energy of 1283 cm–1. These satellite transitions are A(ns2S1/2) + CF4(ν3 = 0) + hν → A((n – 1)d2D3/2,5/2) + CF4(ν3 = 1) and A(ns2S1/2) + CF4(ν3 = 0) + hν → A((n + 1)s2S1/2) + CF4(ν3 = 1), where A = K, Rb, and Cs. The appearance of an optical coupling between the upper and lower states of these asymptotically (at → ∞) forbidden transitions is shown to be caused by the interaction of the dipole moment of the ν3 = 1 ↔ ν3 = 0 vibrational transition in the CF4 molecule with the dipole moments of the electronic transitions np2P1/2,3/2 ↔ (n – 1)d2D3/2,5/2 and np2P1/2,3/2 ↔ (n + 1)s2S1/2 in an alkali metal atom; as a result of this interaction, the upper state of the satellite transition acquires admixtures of the A(np2P1/2,3/2)CF4(ν3 = 0) resonance states. [ABSTRACT FROM AUTHOR]

Organic semiconductors offer the opportunity to develop intrinsically stretchable skin‐like electronics for future applications. However, the lack of intrinsically stretchable materials is still a fundamental challenge, originating from the brittle nature of most organic semiconductors with the fracture strain at a few percent (<10%). Here, a stretchable semiconductor composite is reported by blending the brittle poly[4‐(4,4‐dihexadecyl‐4H‐cyclopenta[1,2‐b:5,4‐b′]dithiophen‐2‐yl)‐alt‐[1,2,5]thiad‐iazolo [3,4‐c] pyridine] (PCDTPT) semiconductor with the crack‐onset strain only at 5% and the styrene‐ethylene‐butylene‐styrene elastomer. This blend films present the increased crack‐onset strain up to 182% and superior optical transparency (>95% at 550 nm), with mobility as high as 2.31 cm2 V−1 s−1. The depth‐dependence light absorption spectra and the conductive atomic force microscopy images in horizontal and vertical directions of the blend film confirm the nonuniform distribution of PCDTPT fibers with sandwiched structure, which weakens the effect of device configuration on mobility. Compared with the conventional uniform film, the sandwiched film weakens the effect of device configuration on mobility. The fully transparent stretchable transistors with the blend films show the outstanding ductility and high optical transparency. This work opens up a feasible path for brittle organic semiconductors used in the transparent stretchable transistor, presenting their promising potential in future see‐through skin‐like electronics. [ABSTRACT FROM AUTHOR]

The local geometry, electronic structure, and vibrational features of three vicinal double interstitial defects in diamond, ICIC, ICIN, and ININ, are investigated and compared with those of three "simple" ⟨100⟩ interstitial defects, ICC, ICN, and INN, previously reported by Salustro et al. [Phys. Chem. Chem. Phys. 20, 16615 (2018)], using a similar quantum mechanical approach based on the B3LYP functional constructed from Gaussian-type basis sets, within a supercell scheme, as implemented in the CRYSTAL code. For the first time, the Fermi contact term and hyperfine coupling tensor B of the four open shell structures, ICIC, ICIN, ICC, and ICN, are evaluated and compared with the available experimental EPR data. For the two double interstitial defects, the agreement with experiment is good, whereas that for the single interstitials is found to be very poor, for which a likely reason is the incorrect attribution of the EPR spectra to uncertain atomic details of the micro-structure of the samples. The infrared spectra of the three double interstitial defects exhibit at least two peaks that can be used for their characterization. [ABSTRACT FROM AUTHOR]

This article deals with the extension of the relativistic double-ionization equation-of-motion coupled-cluster (DI-EOMCC) method [H. Pathak et al. Phys. Rev. A 90, 010501(R) (2014)] for the molecular systems. The Dirac–Coulomb Hamiltonian with four-component spinors is considered to take care of the relativistic effects. The implemented method is employed to compute a few low-lying doubly ionized states of noble gas atoms (Ar, Kr, Xe, and Rn) and Cl2, Br2, HBr, and HI. Additionally, we presented results with two intermediate schemes in the four-component relativistic DI-EOMCC framework to understand the role of electron correlation. The computed double ionization spectra for the atomic systems are compared with the values from the non-relativistic DI-EOMCC method with spin–orbit coupling [Z. Wang et al. J. Chem. Phys. 142, 144109 (2015)] and the values from the National Institute of Science and Technology (NIST) database. Our atomic results are found to be in good agreement with the NIST values. Furthermore, the obtained results for the molecular systems agree well with the available experimental values. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the initial corrosion behavior of pure Mg, AZ31 and AZ91 alloys in phosphate buffer solution (PBS) and to characterize the features in corrosion type and resistance of the corrosion product layer. Design/methodology/approach: The scanning electron microscopy, equipped with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy have been used to characterize the as-corroded samples. Besides, the Mg2+ concentration in PBSs has been determined by inductively coupled plasma atomic emission spectrum. Findings: It has been found that pure Mg suffers pit corrosion, and AZ31 initially undergoes pit corrosion and then uniform corrosion dominates with an extended immersion duration. However, AZ91 exhibits the uniform corrosion with the highest corrosion rate among the three materials. Besides, the corrosion product layer on AZ31 has the best compactness and corrosion resistance. Originality/value: The findings add depth in understanding the corrosion of pure Mg and its alloys in PBS and also have guiding significance in exploring the effects by alloyed elements to develop new biomaterials with better performance. [ABSTRACT FROM AUTHOR]

We present a thermal velocity sampling method for calculating Doppler-broadened atomic spectra, which more efficiently reaches convergence than regular velocity weighted sampling. The method uses equal-population sampling of the 1D thermal distribution, sampling the "inverse transform" of the cumulative distribution function, and is broadly applicable to normal distributions. We also discuss the efficiency by eliminating velocity classes, which do not significantly contribute to the observed atomic lines, and comment on the application of this method in two- and three-dimensions. [ABSTRACT FROM AUTHOR]

At temperatures below the onset of vacancy migration, metals exposed to energetic ions develop dynamically fluctuating steady-state microstructures. Statistical properties of these microstructures in the asymptotic high exposure limit are not universal and vary depending on the energy and mass of the incident ions. We develop a model for the microstructure of an ion-irradiated metal under athermal conditions, where internal stress fluctuations dominate the kinetics of structural evolution. The balance between defect production and recombination depends sensitively not only on the total exposure to irradiation, defined by the fluence, but also on the energy of the incident particles. The model predicts the defect content in the high dose limit as an integral of the spectrum of primary knock-on atom energies, with the finding that low energy ions produce a significantly higher amount of damage than high energy ions at comparable levels of exposure to radiation. [ABSTRACT FROM AUTHOR]

Neutrino scattering on a target at low-energy transfer is one of the basic tools for searching for neutrino electromagnetic properties. We consider the effects of the neutrino millicharge and magnetic moment on the atomic recoil spectrum in elastic neutrino–atom scattering. The results of our calculations of differential cross sections for elastic collisions of tritium neutrinos with the H, 2H, 3He, and 4He atomic targets show that the corresponding experiments can achieve sensitivity to the indicated neutrino electromagnetic characteristics by orders of magnitude better than the available measurements of elastic neutrino–electron and neutrino–nucleus collisions. [ABSTRACT FROM AUTHOR]

Definition: 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 = 2 π c / 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. [ABSTRACT FROM AUTHOR]

The adsorption behavior of atomic oxygen and molecular O2 on the 3C–SiC(1 1 0) surface is investigated by first‐principles calculations. The atomic O prefers to be adsorbed at the C top site (C–O) with adsorption energy of −1.95 eV after zero‐point energy correction, followed by the C–O–Si bridge site, Si–O–Si bridge site, and the Si top site (Si–O) with adsorption energies of −1.46, −1.36, and −1.13 eV, respectively. The molecular O2 separately trapped by the second nearest neighboring C and Si atoms (C–O–O–Si, M4 type) is the most stable configuration with the adsorption energy of −2.46 eV, which is followed by the Si–O–O–Si (M5 type), C–O–O–Si (M3 type), O–Si–O (M2 type), and Si–O=O (M1 type) configurations with the adsorption energies of −2.24, −1.87, −1.07, and −0.75 eV, respectively. All these molecular O2 adsorption configurations exhibit high tendency to dissociate with the dissociation barriers range of 0.09–0.19 eV. The adsorbed atomic O seems to be easily trapped at the C–O site due to the extremely low diffusion barrier. In addition, the infrared spectra of all the atomic O and molecular O2 adsorption configurations are predicted and compared with available experimental observations. [ABSTRACT FROM AUTHOR]

Mining and exploration companies routinely use four-acid digestion (4AD), inductively coupled plasma, atomic emission spectra/mass spectrometry methods from commercial assay laboratories for analysing drill and rock samples for lithogeochemical assessment and resource reporting. This method is also known to exhibit lower recovery of elements hosted by resistate minerals. To assess the impact of lower recoveries on lithogeochemical interpretation, a suite of commonly used elements for lithogeochemical analysis (high-field-strength elements Zr, Hf, Nb, Ta, Ti and Eu and transition elements V and Sc) was analysed by 4AD and alkali fusion/acid digestion (AFAD). Lower recoveries in the 4AD relative to the AFAD were recorded for Zr, Hf, Nb, Ta, Ti and Eu; Sc and V reported similar concentrations for both decomposition methods. Despite the lower recoveries for Nb, Ta and Ti, element ratios were largely preserved with the 4AD method due to the recoveries covarying at a 1:1 ratio. A plot of Ti/Nb against V/Sc was found to be largely unaffected by decomposition method, producing similar compositional classifications between the two digestion methods. Use of the Eu anomaly (Eu/Eu*) to determine plagioclase fractionation was also found to be unaffected by decomposition method. In contrast, a standard Zr/Ti v. Nb/Y discrimination plot produced incorrect classifications with 4AD producing more mafic and alkaline classifications relative to the AFAD method. Magmatic fertility interpretations utilizing Zr/Hf were also found to be affected in the 4AD results due to the lower recovery of Zr relative to Hf. This resulted in a bias in the 4AD results and produced false-positive anomalism in fertility assessments. Multiple decomposition methods including combinations of acid and fusion methods are recommended for lithogeochemical analysis utilizing large regions of the periodic table. However, if only 4AD data are available, plots such as Ti/Nb v. V/Sc and Nb/Ta, which preserve their ratios, can be used for lithogeochemical classification. Supplementary material: Wholerock geochemical data and detailed methods are available at https://doi.org/10.6084/m9.figshare.c.6444444 [ABSTRACT FROM AUTHOR]

Process monitoring and control methods during direct metal deposition (DMD) ensure consistent manufacturing quality of the product. Naturally occurring optical process emissions provide selective and specific element lines, which can be investigated by optical spectrometers. However, DMD processes are mainly characterized by thermal conduction. Hence, the resulting optical emission lines have low intensities. The aim of this work is to investigate the spectral lines and determine the required resolution of the spectrometer. Two spectrometers coupled by a bifurcated optical fiber were used simultaneously (resolution = approx. 47 pm FWHM at 522 nm and 55 pm FWHM at 407.5 nm and resolution = 0.73 nm FWHM). A parameter study with varying process parameters using Co-Cr-based (MetcoClad21) powder on low-alloyed tool steel C45W (1.1730) substrate material was conducted. Peaks occurring in spectral data were assigned to specific element emission lines by using data from the NIST atomic spectra database. All identified element lines were non-ionized elements. Cr I, Fe I and Mn I lines in particular were frequently observed. The occurrence of element emission lines as well as the peak intensity ratios for specific elements was compared with the cross-sectional dimensions including height, weld depth and dilution. It has been shown that the occurrence and intensity of emission lines correlate with the process parameters, especially the laser power. Furthermore, the dilution of a deposition track correlates with the occurrence and intensity of an identified Fe I emission line, represented by a Fe-Cr peak intensity ratio. [ABSTRACT FROM AUTHOR]

Previously reported atomic data (spectral lines, wavelengths, energy levels, and transition probabilities) were collected and systematically analyzed for Cs VI. The present theoretical analysis was supported by extensive calculations made for Cs VI with a pseudo-relativistic Hartree–Fock (HFR) method together with the superposition of configuration interactions implemented in Cowan’s codes. In this work, all previously reported energy levels and their (allowed) transition assignments were confirmed. A critically evaluated set of optimized energy levels with their uncertainties, observed and Ritz wavelengths along with their uncertainties, and theoretical transition probabilities with their estimated uncertainties were presented in the compilation. In addition to this, we determined the radiative transition parameters for several forbidden lines within the ground configuration 5s25p2 of Cs VI.

Atoms and ions remain in some long-lived excited levels for much longer than in typical “normal” levels, but not forever. Various cases of this so-called metastability that occur in multiply or even highly charged ions are discussed in a tutorial review, as well as examples of atomic lifetime measurements on such levels, their intentions, and some present and future applications.

The electric field in the head of the plasma bullet (ionization wave) in a cold atmospheric pressure plasma jet is measured using the Stark polarization spectroscopy technique, a noninvasive method. The jet is driven by 1 μ s long voltage pulses at 6 kV amplitude and 5 kHz frequency, and a helium gas flow of 1.5 slm. Two helium lines (447.1 nm and 492.2 nm) are studied, from which the peak-to-peak wavelength difference between the allowed and forbidden band of the spectral lines is determined. The full derivation to obtain the electric field from this peak-to-peak difference is included in this paper. The electric field is determined both inside and outside the capillary of the jet, up to about 2 cm in the effluent of the jet. Measurements are performed on the freely expanding jet, but especially the influence is studied when a target is placed in front of the plasma jet. Targets with different properties are used: insulating (polyvinyl chloride, PVC), conducting (copper), liquid (distilled water and saline), and organic (chicken breast). It is found that a target changes the electric field of the plasma jet and thus changes the plasma itself. This change depends on the dielectric constant or conductivity of the target: a higher dielectric constant or higher conductivity yields a higher electric field. For a low dielectric constant (ϵ r ≈ 3), the change in the electric field is negligible. Decreasing the distance between the target and the capillary to below 2 cm yields an increase in the electric field. [ABSTRACT FROM AUTHOR]

A comparative analysis was performed for 13C NMR chemical shifts of C-4 and C-4a (or C-5) atoms in previously synthesized pyrido[2,3-d]-pyrimidin-5-ones, pyrido[2,3-d]pyrimidin-7-ones, pyrimido[4,5-d]pyrimidines, and 5-acetylpyrimidines containing methylsulfanyl, methylsulfonyl, butoxy, and amino groups at position 4. It was possible to determine the type of heteroatom (sulfur, oxygen, or nitrogen) bonded to the C-4 carbon atom on the basis of chemical shifts observed for C-4a carbon atom in the spectra of fused heterocycles or C-5 carbon atom in the spectra of pyrimidines. At the same time, the chemical shift values of C-4a (or C-5) atoms practically did not depend on the particular sulfur-containing functionality: sulfanyl or sulfonyl group. A significant upfield shift was observed for the C-4 atom in 13C NMR spectra of sulfones compared to the spectra of compounds containing a methylsulfanyl moiety. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is an atomic spectrum analysis method with the advantage of simple, rapid, and multi-element analysis. It has great application potential for the analysis of heavy metal elements in medicinal herbs. However, when LIBS is used to analyze mercury (Hg) in medicinal herbs, the high recombination rate of mercury plasma and the selective quenching of mercury atomic emission lines by oxygen will reduce the analytical sensitivity. In this work, nanoparticle-enhanced LIBS (NE-LIBS) combined with argon (Ar) purging was used to improve the analytical sensitivity of Hg in the medicinal herb dried tangerine peel. The deposition of nanoparticles (NPs) was optimized by surface superhydrophobic treatment of the sample. The effects of the size, shape, and surface concentration of the NPs on the LIBS signal intensity were analyzed. The flow rate of the Ar jet was optimized. The results showed that detection stability was improved by surface superhydrophobic treatment. The spectral intensity of Hg I 253.65 nm was increased 6.19 times under the optimized parameters of 40 nm diameter nanocages with a surface concentration of 1.77 × 10−3 mg cm−2 and an Ar jet flow rate of 15 L min−1. The calibration curves of Hg I 253.65 nm were constructed under the optimized parameters. According to the calibration curves, the coefficient of determination (R2), root mean square error of cross validation (RMSECV), and limit of detection (LoD) of NE-LIBS combined with Ar purging were 0.9954, 3.47 mg kg−1, and 2.46 mg kg−1, respectively. Compared with traditional LIBS methods, NE-LIBS combined Ar purging improved the analytical sensitivity of Hg in medicinal herbs, with the LoD improved by 9.73 times. The practicability of the method was demonstrated by analyzing dried tangerine peels from other regions and the relative errors were in the range of 0.52–2.70%. [ABSTRACT FROM AUTHOR]

Within the framework of the density functional theory and the ab initio pseudopotential, we have obtained the spatial distributions of the valence electrons density, the electron energy spectra and the atom charge states of 1D-coordination polymers based on arendiyl-bisphosphinic acids and metal ions. Formation of one-dimensional polymer chains takes place under participation of strong intermolecular bonds. [ABSTRACT FROM AUTHOR]

Atheoretical particle-number conserving quantum field theory based on the concept of imaginary time is presented and applied to the scenario of a coherent atomic laser field at ultra-cold temperatures. The proposed theoretical model describes the analytical derivation of the frequency comb spectrum for an atomic laser realized from modeling a coherent atomic beam of condensate and non-condensate quantum field components released from a trapped Bose-Einstein condensate at a given repetition phase and frequency. The condensate part of the atomic vapor is assumed to be subjected to thermal noise induced by the temperature of the surrounding thermal atomic cloud. This new quantum approach uses time periodicity and an orthogonal decomposition of the quantum field in a complex-valued quantum field representation to derive and model the quantum field's forward- and backward-propagating components as a standing wave field in the same unique time and temperature domain without quantitative singularities at finite temperatures. The complex-valued atom laser field, the resulting frequency comb, and the repetition frequency distribution with the varying shape of envelopes are numerically monitored within a Monte Carlo sampling method, as a function of temperature and trap frequency of the external confinement. [ABSTRACT FROM AUTHOR]

Due to its electro-optical properties, the delafossite CuAlO2 is a potential candidate for energy conversion. Here, employing the Density Functional Theory (DFT), we performed the first-principles study of the electronic, dielectric, and dynamical properties of CuAlO2. The structural study shows a good agreement between the experimental and theoretical data. The electronic properties of CuAlO2 are investigated by the calculation of the band structure and the total and partial density of states. The optical gap (1.95 eV), indirectly allowed, is slightly over-estimated compared to the experiment value (1.96 eV), determined by diffuse reflectance. The diamagnetism conforms with closed-shell configurations of Cu+ (3d10) and Al3+ which obey the octet and 18 electron rules, respectively. However, a Curie constant of 0.014 uem CGS mol−1 with a slight paramagnetism is ascribed to the small amount of inserted O2− species with concomitant oxidation of Cu+ to Cu2+. The calculated Born effective charges are close to the nominal charges of the ions. Calculation of the full phonon dispersion spectrum with the atomic displacements allows a better understanding of the vibrational properties of CuAlO2: The Raman active modes (Eg and A1g) exhibit an O-site character while the infrared active modes (A2u and Eu) are featured by a combined shift of the three atoms. The photo-electrochemistry confirms the p-type behavior with a valence band edge of 5.35 eV below a vacuum, made up of Cu+: 3d orbital and far from the theoretical value of 6.9 eV. The discrepancy can be due to the fact that theoretical values are calculated at 0 Kelvin and at the point of zero charge (pzc). [ABSTRACT FROM AUTHOR]

Exploration of the tractable size basis set that can provide reliable estimates of computed properties for systems containing heavy elements has been the subject of interest in quantum chemistry over many decades. In this connection, the recently developed segmented all-electron relativistically contracted (SARC) basis set proposed by Rolfes et al. [J. Comput. Chem. 41, 1842 (2020)] appears to be worth studying. In the present attempt, ground and excited state properties of the Ag atom is computed on this basis at the Fock-space multi-reference coupled cluster (FSMRCC) level of theory with four-component relativistic spinors. The computed quantities resulting from the SARC basis are subsequently compared with those obtained using an even-tempered basis to assess the efficacy of the SARC basis. Computations have also been performed with the extended SARC basis to improve the quality of the property of interest. The accuracy of the computed quantities such ionization energy, electron affinity, excitation energies, etc., obtained using the SARC basis at the FSMRCC level of theory demonstrates that the SARC basis (particularly the extended one), which is primarily designed for quantum chemical calculations at the two-component scalar relativistic level for systems containing heavy atoms, can be used for fully relativistic calculations. The magnetic dipole hyperfine structure constant A , oscillator strengths f and transition rates Afi calculated using the SARC basis also agree well with the experiment and with the available theoretical estimates. [ABSTRACT FROM AUTHOR]

Abstract—We present the first part of the survey of the results of spectroscopic observations of mirides in the optical and near infrared ranges. The main phenomenological schemes and models are listed. The published results are supplemented by spectroscopic observations and calculations performed at the SAO RAS. [ABSTRACT FROM AUTHOR]

A multitude of weaker Fe IX lines have been predicted in the vicinity of the strong 171 Å line that dominates the spectra of many astrophysical and laboratory sources. Some of these weaker lines have only recently been identified in the laboratory, albeit some only tentatively. Here, we present measurements on the Livermore EBIT-I electron beam ion trap that span the region from 170.0 to 173.6 Å, which surrounds the 171 Å line. The measurements stepped through electron beam energy to determine the charge state of iron associated with each observed feature. Moreover, we have minimized the presence of oxygen in the trap, because oxygen lines obscured possible Fe IX lines in past measurements and prevented their identification. Our measurement confirms formerly tentative identifications and adds several new assignments. [ABSTRACT FROM AUTHOR]

The Fe IX spectrum features two lines in the extreme ultraviolet whose ratio has been rated among the best density diagnostics in the solar spectrum. One line is an E 1 -allowed intercombination transition at 244.909 Å, the other an E 1 -forbidden M 2 transition at 241.739 Å. Employing a medium and a high resolution spectrometer at the Livermore EBIT-I electron beam ion trap, we have observed the line pair in the laboratory for the first time. Using a CHIANTI model computation, the observed line ratio yields a value of the electron density that is compatible with typical densities in our device. [ABSTRACT FROM AUTHOR]

Atomic lifetime measurements span a wide range, from attoseconds to years. The frontier of exploratory lifetime measurements, presently, is in the long part of the above time range, with an eye on astrophysical problems. In a combination of review paper, tutorial, and Editorial, the physical environments and experiments are discussed, in which the results of such lifetime measurements matter. Although accurate lifetime measurement results are important for our understanding of atomic structure and dynamics, and for the diagnostics of various plasma environments, the order of magnitude is often precise enough to see why time resolution may be of interest in an experiment, from laser-produced plasmas of high densities to planetary nebulae of very low densities. [ABSTRACT FROM AUTHOR]

Exploring the physical characteristics of lightning discharge channels based on spectrum can help to reveal the microscopic mechanism of the discharge process and provide a theoretical basis for lightning protection research. According to the spectra of six cloud-to-ground lightning return stroke processes and plasma conduction theory, we investigated the evolution of the total intensity of ionic and atomic lines in the spectra, conductivity, and other parameters along the discharge channel at different stages of the return stroke. The results show that the intensity of ionic lines in the spectrum present an obvious decaying trend with increasing height along the channel during the initial current-rise phase of the return stroke. In the later stages, the decay of ionic line intensity along the channel height slowed down. The intensity of the atomic lines varied slightly with increasing height along the channel during the entire return stroke process. The different space-time evolution characteristics of the spectral line intensity with different excitation energies reflect the differences in the mechanism of light radiation in the core current-carrying and surrounding thermal channels. The spectral characteristics further confirm that the ionic line with higher excitation energy directly relates to the physical process in the core current-carrying channel, and its intensity can roughly reflect the change in current along the channel. The attenuation of the return stroke current along the channel was mainly manifested in the initial stage of the return stroke. The decay rate of conductivity along the channel height is slower than that of the ionic line intensity throughout the return stroke stage, which is related to the channel diameter, it is another key parameter affecting the current transmission in the discharge channel. • For the first time, space-time evolution of light radiation in return stroke process are investigated simultaneously. • Spectral analysis infers that current attenuation along channel mainly manifests in the initial stage of return stroke. • According to the evolution of spectrum and conductivity along the discharge channel, channel radius is a key parameter related to current transmission. [ABSTRACT FROM AUTHOR]

We describe the results of currently topical investigations of the method used for the production of activated carbon from the biomass wastes with the help of microwave carbonization. As compared with ordinary carbonization in thermal furnaces, the procedure of microwave carbonization proves to be a more energy-efficient and environmentally friendly method. However, at present, the problem of guaranteeing the required reproducibility and thermal stability of this process remains unsolved. In the course of microwave irradiation, the temperature of the biomass samples continuously varies and, moreover, complex physicochemical processes run inside these samples. Therefore, in order to determine optimal modes of microwave treatment, it is necessary to know the temperature dynamics of biomass samples. It is proposed to determine the required temperature dynamics of biomass samples by the method of spectral pyrometry. The method is based on the separation of the sections of thermal radiation spectra of the samples that coincide with the Planck function with variable temperature. In these sections, the samples exhibit the properties of gray radiators. The method proves to be efficient for an unknown emission coefficient continuously varying as a function of microstructure, chemical composition, and phase state of the sample. The sample irradiated with microwaves is a weighted amount of cotton linter treated by orthophosphoric acid with a weight of 1 g. The source of microwaves is a magnetron-type generator with a maximum output power of 600 W and a working frequency of 2450 MHz. The thermal spectra of irradiated samples were recorded by using small-size spectrometers operating in visible (350–760 nm) and near infrared (650–1050 nm) bands. The time of irradiation of samples with microwaves varied within the range 60–180 sec. The obtained spectra are processed with the help of the Spectral Pyrometry program, which reads and processes the recorded spectrum, constructs the plots on the Planck and Wien coordinates, and computes temperatures. The analysis of the accumulated results reveals different types of spectra of thermal radiation of the irradiated sample, namely, the spectra similar to the spectra of a perfect radiator, spectra with different temperature zones of the sample, and spectra with atomic lines and molecular bands. The accumulated results prove to be useful for the investigation of the influence of microwaves on various objects, for the study of processes running in the course of carbonization of the biomass, and for the development of more efficient modes aimed at getting activated carbons by the microwave method. [ABSTRACT FROM AUTHOR]

In this paper, density functional theory is used to study the electronic, magnetic and light absorption behavior of the Non-metallic atoms adsorbed and doped Ga 2 O 3 systems. The results show that the Non-metallic atoms adsorbed and doped can adjust the band structure and magnetic properties of Ga 2 O 3. The Non-metallic atoms adsorbed and doped Ga 2 O 3 systems will contribute to the design of nano-spintronics devices. In addition, charge transfer occurs between Ga 2 O 3 and Non-metallic atoms, indicating a covalent bond feature between Non-metallic atoms and uncoordinated atoms. In particular, the absorption spectra of the Non-metallic atoms adsorbed and doped Ga 2 O 3 systems have many strong visible light absorption peaks. The Non-metallic atoms adsorbed and doped Ga 2 O 3 systems have a wide regulatory range in the solar spectrum. These findings are of great significance for optimizing the properties of Ga 2 O 3 materials and developing new applications. [ABSTRACT FROM AUTHOR]

Energy levels, lifetimes, oscillator strengths and transition probabilities for the multicharged oxygen like Cl X ion have been calculated with the configuration expansion: 2s 2 2p 4 , 2p 6 , 2s 2 2p 3 3p, 2s2p 5 , 2s 2 2p 3 3s, 2s 2 2p 3 4s, 2s 2 2p 3 3d, 2s 2 2p 3 4d, 2s2p 4 3s and 2s2p 4 4s. We used two methods in the calculations: the Hartree–Fock pseudo-relativistic approach and the Thomas–Fermi–Dirac–Amaldi potential approach using the Cowan and the AUTOSTRUCTURE atomic structure codes respectively. Results have been compared with available experimental data from the National Institute of Standards and Technology Atomic Spectra Database (NIST-ASD) and with results from other available calculations. There is a great lack of atomic structure data of Cl X and obtained new data will be important for physics applications and astrophysical modeling. [Display omitted] • Energy levels and lifetimes for the lowest fine-structure levels of Cl X calculated. • Obtained energies and lifetimes compared with experimental and theoretical data. • Calculations of the oscillator strengths and transition probabilities of the Cl X. • Obtained transition parameters compared with experimental and other theoretical data. [ABSTRACT FROM AUTHOR]

Graphene-based nanomaterials have attracted significant attention for their potentials in biomedical and biotechnology applications in recent years, owing to the outstanding physical and chemical properties. However, the interaction mechanism and impact on biological activity of macro/micro biomolecules still require more concerns and further research in order to enhance their applicability in biosensors, etc. Herein, an integrated method has been developed to predict the protein bioactivity performance when interacting with nanomaterials for protein-based biosensor. Molecular dynamics simulation and molecular docking technique were consolidated to investigate several nanomaterials: C60 fullerene, single-walled carbon nanotube, pristine graphene and graphene oxide, and their effect when interacting with protein. The adsorption behavior, secondary structure changes and protein bioactivity changes were simulated, and the results of protein activity simulation were verified in combination with atomic force spectrum, circular dichroism spectrum fluorescence and electrochemical experiments. The best quantification alignment between bioactivity obtained by simulation and experiment measurements was further explored. The two proteins, RNase A and Exonuclease III, were regarded as analysis model for the proof of concept, and the prediction accuracy of protein bioactivity could reach up to 0.98. The study shows an easy-to-operate and systematic approach to predict the effects of graphene-based nanomaterials on protein bioactivity, which holds guiding significance for the design of protein-related biosensors. In addition, the proposed prediction model is not limited to carbon-based nanomaterials and can be extended to other types of nanomaterials. This facilitates the rapid, simple, and low-cost selection of efficient and biosafe nanomaterials candidates for protein-related applications in biosensing and biomedical systems. Fig. 1. Schematic illustration of in silico prediction. (a) Structure diagram of four GBNMs. (b) The conformational change process of protein to nanomaterial by molecular dynamic simulation. (c) The bioactivity simulation of protein by molecular docking. [Display omitted] • Interaction between protein and nanomaterial is crucial for biosensor performance. • A model integrating molecular dynamic and docking simulation predicts the bioactivity. • A model directly predicts protein activity on nanomaterials rather than by conformation changes. • The prediction accuracy of protein bioactivty could reach up to 0.98. • The prediction model can be extended to other types of protein and nanomaterials. [ABSTRACT FROM AUTHOR]

Network science provides a universal framework for modeling complex systems, contrasting the reductionist approach generally adopted in physics. In a prototypical study, we utilize network models created from spectroscopic data of atoms to predict microscopic properties of the underlying physical system. For simple atoms such as helium, an a posteriori inspection of spectroscopic network communities reveals the emergence of quantum numbers and symmetries. For more complex atoms such as thorium, finer network hierarchies suggest additional microscopic symmetries or configurations. Furthermore, link prediction in spectroscopic networks yields a quantitative ranking of yet unknown atomic transitions, offering opportunities to discover new spectral lines in a well-controlled manner. Our work promotes a genuine bi-directional exchange of methodology between network science and physics, and presents new perspectives for the study of atomic spectra.

We present extensive energy levels (1110 levels) and transition data for the Pr  iv. We also show the effect of such atomic data on opacity for neutron star (NS) merger. We performed energy spectra and transition data calculations using the GRASP2018 package, which is based on the multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction methods. Using the GRASP2018 data, the opacities in the NS merger ejecta containing pure Pr are calculated. Energy levels are compared with recommended values from the NIST Atomic Spectra Database and other available works. Furthermore, electric dipole (E1) transition data, line strengths, weighted oscillator strengths, and transition rates are computed between the above levels. We estimate the uncertainties of the computed line strengths giving the accuracy class. The computed line strengths are also compared with other theoretical computations. We proposed few ways to estimate the uncertainties of the line strengths of the E1 transitions. Our calculation for opacity for a typical condition of NS merger ejecta at t ∼ 1 d shows that the Planck mean opacity of Pr3 + reaches |$\sim 1\, \rm cm^{2}\, g^{-1}$| at |$T\, \sim \, 15000$| K. The opacity is higher than that by the previous studies, thanks to the higher completeness of the atomic data. We also highlight the importance of accurate atomic data for the opacity by comparing it with the opacity using the atomic calculation from HULLAC. Moreover, we identify the important configurations, especially for the transitions between the high-lying levels for the opacity of 3+ ionized lanthanides. [ABSTRACT FROM AUTHOR]

Radical polymerization reactions were employed to synthesize thermo‐responsive poly(N‐isopropylacrylamide‐co‐1‐vinylimidazole), p (NIPAM‐co‐VIm), hydrogels at room temperature. A postquaternized cross‐linking strategy was reported to fabricate thermo‐sensitive quaternized‐p (NIPAM‐co‐VIm) ionic hydrogels, Q‐p (NIPAm‐co‐VIm). Combination of methods (high‐resolution X‐ray photoelectron spectroscopy, dynamic light scattering, and atomic absorption spectroscopy) was employed to characterize the composite material. Following the concept of a "green chemistry," the oxidation of alcohols/olefins was carried out in aqueous solution by using nanocomposites, p (NIPAM‐co‐VIm) and Q‐p (NIPAM‐co‐VIm). It was found that the catalytic activity of the metal nanocomposite can be modulated by the lower critical solution temperature (LCST) of particles. The catalyst showed improved catalytic activity above LCST. Quaternized composites showed higher catalytic activity than unquaternized counterparts, due to their high hydrophobicity, effective interactions between substrates and catalyst, and high flexibility. In addition, we demonstrated that the catalytic activity of the nanocomposites can be tuned by the volume phase transition within the hydrogel by using the catalytic reduction of 4‐nitrophenol/nitrobenzene, NP/NB, as the hydrophilic/hydrophobic substrates model. For 4‐NP, with an increase in temperature from 25°C to 35°C (

The frequent occurrence of quality and safety incidents in agricultural products has intensified consumers' concerns. Since laser-induced breakdown spectroscopy (LIBS) is a promising, versatile atomic spectrum analysis technique for the analysis of various elements, which has the advantages of simple sample preparation (compared to reference methods), quick analysis, convenient operation and non-contact detection, it has gradually become a research focus in the field of agricultural product inspection. This work reviews applications of LIBS in the analysis of agricultural products in recent years, and aims at sample preparation techniques for various types of agricultural products to improve the quality of analytical data, and the capability of LIBS for qualitative and quantitative analysis of different samples. Finally, LIBS holds potential for real-time elemental analysis of agricultural products and practical applications in precision farming. This could be beneficial for immediate diagnoses of contaminated food and increasing agricultural production while minimizing environmental impacts. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy refers to the radiation spectrum formed by the vaporization and ionization of samples under high-temperature conditions. It is a new technology for detecting and analyzing the composition and content of materials. However, this technology is not yet very mature; in this regard, this paper proposes a quantitative study of atomic spectroscopy using laser-induced technology. On this basis, a method using laser-induced breakdown spectroscopy is proposed, and its quantitative analysis and application are carried out in detail. The laser-induced breakdown technology uses a high-power pulsed laser to form a plasma on the surface of the test piece and analyzes its radiation spectrum to obtain the composition and content of its elements. It also used the laser-induced breakdown technique to quantitatively analyze the Ti-doped Al2O3 ceramic system. Through the quantitative analysis of constant laser and constant plasma temperature, the linear correlation coefficient R2 of the calibration curve calculated with constant plasma temperature is obtained as 0.985, and the relative error is 5.3%. This paper uses a fixed laser pulse amplification voltage, the linear coefficient of the proportional relationship curve is only 0.92, and the error rate is 8.9%. By comparing the two curves, the Ti proportional curve obtained by a fixed plasma temperature is obtained in this paper. Its linearity is better than the Ti scaling curve obtained by constant laser voltage. [ABSTRACT FROM AUTHOR]

Amusia and Kheifets in 1984 introduced a Green's function formalism to describe the effect of many-electron correlation on the ionization spectra of atoms. Here, we exploit this formalism to model the shake-off (SO) process, leading to the non-sequential single-photon two-electron ionization (double photoionization—DPI) of closed-shell atomic targets. We separate the SO process from another knock-out (KO) mechanism of DPI and show the SO prevalence away from the DPI threshold. We use this kinematic regime to validate our model by making a comparison with more elaborate techniques, such as convergent and time-dependent close coupling. We also use our model to evaluate the attosecond time delay associated with the SO process. Typically, the SO is very fast, taking only a few attoseconds to complete. However, it can take much longer in the DPI of strongly correlated systems, such as the H − ion as well as the subvalent shells of the Ar and Xe atoms and Cl − ion. [ABSTRACT FROM AUTHOR]

Enhanced emission was observed in the laser-induced breakdown spectroscopy (LIBS) atomic emission spectra of bacterial cells deposited upon a nitrocellulose filtration medium in the presence of one-micron silver microparticles. A deposition chamber was constructed that allowed a uniform coating of the filter with trace amounts of silver microparticles. Masses from 10 to 100 μg were deposited in a circular area of 52.18 mm2. A 30 s deposition time was used for all experiments resulting in a mass deposition of 39 μg ± 17 μg. This mass coverage on the filter provided for a single laser shot silver mass ablation of 3.3 ng per laser shot. LIBS spectra were acquired with single-shot 1064 nm laser pulses from specimens of E. coli, M. smegmatis, and E. cloacae deposited on both microparticle-coated filters and blank filters. An increase in emission intensity for all elements detected in the bacterial LIBS spectrum as well as the carbon emission which derives in part from the nitrocellulose filter medium was observed due to the ablation with silver microparticles relative to the intensity measured from the ablation of bacterial cells deposited on a blank filter. The ratio of emission intensity with microparticles to emission intensity without microparticles was measured to be 3.6 for phosphorus, 4.5 for magnesium, 5.3 for calcium, 4.0 for sodium, and 1.2 for carbon. An enhancement in LIBS emission intensity in the range of 1–10 was observed for all the spectra, with an average enhancement ratio of 4.3. Graphical Abstract [ABSTRACT FROM AUTHOR]

A double crystal assembly (DCA) for multiple atomic spectra measurements, including helium-like Ar and hydrogen-like Ar, and other impurity lines are applied for the x-ray imaging crystal spectrometer in Korea Superconducting Tokamak Advanced Research. The DCA expands measurable wavelengths much wider so that cross comparisons of the ion temperature and toroidal rotation between two different atomic states are possible. The recent experimental comparison studies for the ion temperature and toroidal rotation of helium-like Ar and hydrogen-like Ar from the DCA are reported. [ABSTRACT FROM AUTHOR]

We propose a new method for calculating the redshift in galaxies, according to which the amount of redshift in the spectrum of each galaxy consists of two parts: about 2/3 of the redshift is due to the speed of the galaxy moving away from us, and about 1/3 is due to the fact that photons moving in the expanding Universe acquire an additional (non-Doppler) redshift. The additional reddening of photons in the spectrum of the galaxy is due to photons coming to us from the past, when the gravitational potential of the universe was lower, and consequently, the frequencies of atomic spectra were also lower than at present. A scheme of a laboratory experiment is proposed that will allow direct measurement of a non-Doppler (additional) part of the cosmological redshift and demonstrate the very fact of the expansion of the universe in real time in about 15 min. The experiment also makes it possible to measure the expansion rate of the universe and its current gravitational potential. These results will help to significantly refine modern ideas about the age of the universe, and about the amount of dark energy and dark matter in it. [ABSTRACT FROM AUTHOR]

We study the role of disorder in the vibration spectra of molecules and atoms in solids. This disorder may be described phenomenologically by a fractional generalization of ordinary quantum-mechanical oscillator problem. To be specific, this is accomplished by the introduction of a so-called fractional Laplacian (Riesz fractional derivative) to the Scrödinger equation with three-dimensional (3D) quadratic potential. To solve the obtained 3D spectral problem, we pass to the momentum space, where the problem simplifies greatly as fractional Laplacian becomes simply k μ , k is a modulus of the momentum vector and μ is Lévy index, characterizing the degree of disorder. In this case, μ → 0 corresponds to the strongest disorder, while μ → 2 to the weakest so that the case μ = 2 corresponds to "ordinary" (i.e. that without fractional derivatives) 3D quantum harmonic oscillator. Combining analytical (variational) and numerical methods, we have shown that in the fractional (disordered) 3D oscillator problem, the famous orbital momentum degeneracy is lifted so that its energy starts to depend on orbital quantum number l. These features can have a strong impact on the physical properties of many solids, ranging from multiferroics to oxide heterostructures, which, in turn, are usable in modern microelectronic devices. [ABSTRACT FROM AUTHOR]

Parametric modulation is an effective tool to measure the trap frequency and investigate the atom dynamics in an optical dipole trap or lattices. Herein, we report on experimental research of parametric resonances in an optical dipole trap. By modulating the trapping potential, we have measured the atomic loss dependence on the frequency of the parametric modulations. The resonance loss spectra and the evolution of atom populations at the resonant frequency have been demonstrated and compared under three modulation waveforms (sine, triangle and square waves). A phenomenological theoretical simulation has been performed and shown good accordance with the observed resonance loss spectra and the evolution of atom populations. The theoretical analysis can be easily extended to a complex waveform modulation and reproduce enough of the experiments. [ABSTRACT FROM AUTHOR]

There has been strong recent interest related to the large spin–orbit coupling in Pb monolayers on various properties of graphene and other 2D-materials. The underlying physical/chemical origin of the spin–orbit splitting has been discussed in terms of the valence 6p atomic level of the lead atom. Indeed, the photoelectron spectra of the Pb atom were the subject of investigations about 50 years ago in Dave Shirley's laboratory at UC Berkeley. In a paper published in 1975, using He-I UV photoelectron spectroscopy, we reported an unexpected relative intensity ratio for the observed atomic Pb peaks (2P1/2 and 2P3/2) after removal of a 6p valence electron and attributed it to the large spin–orbit interaction in that level. In this contribution, we use the Dirac–Hartree–Fock formalism to reanalyze the complex spectral features reported five years later, for the 5d He-II UV photoelectron spectrum of atomic lead, to extract the 6p valence contribution, which turns out to be significant. Furthermore, we calculate the energy levels of the Pb-dimer at the experimental equilibrium geometry of the molecule to also find the significant contribution of the spin–orbit splitting of the atomic 6p levels in the composition of the valence molecular orbitals of the dimer. Such an approach can be extended to larger systems like monolayers containing lead or other heavy atoms, thus helping in designing 2D-materials with controlled and better targeted properties. [ABSTRACT FROM AUTHOR]

Transition probabilities per time unit in the spectrum of the hydrogen atom confined in a spherical cavity are studied with the Dirac equation. The calculations are performed with simple and accurate expansions of the Dirac components provided by the Lagrange-mesh method with small numbers of scaled Jacobi mesh points. The initial and final states as well as intermediate states occurring in two-photon transitions are described with a single Lagrange mesh. With this simplification, accurate matrix elements are easily computed with the Gauss quadrature associated with the Lagrange–Jacobi mesh. One-photon transitions are considered from the n = 2 and 3 levels. Most transition probabilities increase as a negative power of the confinement radius when it becomes small. The two-photon 2 s 1 / 2 - 1 s 1 / 2 transition stops being the main deexcitation channel of the 2 s 1 / 2 level when the confinement radius decreases below about 15 atomic units. The 2 p 1 / 2 and 2 p 3 / 2 levels come below the 2 s 1 / 2 level and allow a faster one-photon deexcitation. [ABSTRACT FROM AUTHOR]