Spectral Line Intensities Research Articles

Optimization of sample preparation of mono- and bimetallic catalysts based on Sibunit carbon carrier for quantitative analysis by ICP-AES

Composite materials like «Sibunit» are used as carriers for heterogeneous catalysts. These materials exhibit high mechanical strength, chemical purity, high resistance to aggressive environment, and controlled porous structure. The components of such catalysts are noble metals, and their combinations with oxides of some transition metals. An urgent task in their production is to control the content of the active component in the composition of catalysts. This characteristic affects the phase and electronic state of the metal, the structural and textural characteristics of the carbon carrier, and hence determines the activity and selectivity of catalysts during operation. Quantitative chemical analysis thus becomes one of the main methods for controlling the quality of catalysts. Different options for acid decomposition of mono- (Pd/C, Ru/C, Ga/C) and bimetallic (Pd-Ga/C, Pd-Zn/C, Pd-Ru/C, Pd-Ag/C) catalytic systems based on carbon carrier «Sibunit» are considered. The goal of this study is determination of the content of metals by inductively coupled plasma atomic emission spectrometry. The effect of the main operating parameters of the spectrometer on the intensity of sensitive and non-overlapping spectral lines of the elements being determined was studied. Optimal conditions for measuring the analytical signal were chosen. It is shown that for the studied bimetallic systems, with the exception of Pd-Ru/C, it is possible to choose a sample preparation option that allows simultaneous quantitative determination of two components from one sample. The developed method of quantitative analysis is characterized by rather high accuracy. The relative error of the element determination does not exceed 3 %, the relative standard deviation is not more than 5 %. The results of the study can be used to analyze catalysts of similar chemical composition by inductively coupled plasma atomic emission spectrometry.

Geometric Assumptions in Hydrodynamic Modeling of Coronal and Flaring Loops

In coronal loop modeling, it is commonly assumed that the loops are semicircular with a uniform cross-sectional area. However, observed loops are rarely semicircular, and extrapolations of the magnetic field show that the field strength decreases with height, implying that the cross-sectional area expands with height. We examine these two assumptions directly, to understand how they affect the hydrodynamic and radiative response of short, hot loops to strong, impulsive electron beam heating events. Both the magnitude and rate of area expansion impact the dynamics directly, and an expanding cross section significantly lengthens the time for a loop to cool and drain, increases upflow durations, and suppresses sound waves. The standard T ∼ n 2 relation for radiative cooling does not hold with expanding loops, which cool with relatively little draining. An increase in the eccentricity of loops, on the other hand, only increases the draining timescale, and is a minor effect in general. Spectral line intensities are also strongly impacted by the variation in the cross-sectional area because they depend on both the volume of the emitting region as well as the density and ionization state. With a larger expansion, the density is reduced, so the lines at all heights are relatively reduced in intensity, and because of the increase of cooling times, the hottest lines remain bright for significantly longer. Area expansion is critical to accurate modeling of the hydrodynamics and radiation, and observations are needed to constrain the magnitude, rate, and location of the expansion—or lack thereof.

A New Intensity Adjustment Technique of Emission Spectral Analysis When Measured at the Upper Limit of the Dynamic Range of Charge-Coupled Devices

The article presents a method of mathematical correction to be applied to the results of measuring the intensity of spectral lines using charge-coupled devices (CCDs) in the presence of the blooming effect. This technique is particularly applicable in atomic emission spectroscopy. It enables expansion of the dynamic range of spark emission spectrometers and significantly minimizes the result distortions of the measurements taken in the area of high element concentrations. The authors devised a mathematical model and proposed an algorithm to adjust the measured intensity of analytical lines at the photo detector upper limit, in addition to an algorithm for processing data from the spectra recording system. The proposed mathematical algorithm was integrated into the software for the SPAS-02 and SPAS-05 spark spectrometers produced in Russia, and tested in determining the chemical composition of steels. The findings show that the actual dispersion of the analytical line intensity distribution may exceed the measured dispersion by a factor of 1.5, and their intensities may differ by a factor of 2. This algorithm may be implemented in atomic emission spectrometer software and makes it possible to adjust the calibration curves for a range of high alloying element concentrations when the analytical line intensity is at the upper limit of the CCD dynamic range.

Investigation of a Glow Discharge with a Coaxial Hollow Cathode

The article is devoted to the study of the operating modes of a glow discharge with a coaxial hollow cathode in helium and neon gases. It is shown that the burning voltage of a discharge with a coaxial hollow cathode is lower than one with a cylindrical hollow cathode of equal diameter, and the position of the optimal pressure range depends on the width of the annular gap of the cavity. It is noted that the rod current density is 3-5 times higher than the cylinder current density. The insignificant role of the photoelectric effect in the processes of electron emission from the cathode is proved. It is shown that the intensity of the atomic spectral lines of the cathode material increases significantly when a coaxial hollow cathode is used.

Determination of Electrons Temperature and Density For Ag, Zn, and Cu metals using Plasma jet System at atmospheric pressure

Under atmospheric pressure, an argon plasma stream was sustained and its plasma characteristics were examined. The emission spectra of plasma created in a plasma jet system using argon gas were observed for three metals (Ag, Zn, and Cu) for the anode and varied flow rates ranging from 1–4 L/min. at constant voltage, and normal atmospheric pressure. The spectral lines of excited Ar, Ag, Zn, and Cu species were identified at a wavelength of (650–900) nm .The Debye length, sphere, and temperature of an electron are all measured. Optical emission spectrometer (OES) equipment was used to capture the spectrum produced by the plasma at various argon gas flow rates.The temperature and density of the electron (Te) and (ne) ranges for Ar-gas, Ag, Zn, and Cu-anode increased as the stream pace of argon gas to the plasma made by the release current (D.C.) expanded.(1.241- 1.473)eV and (1.93 x1018–6.38 x1018 ) cm-3 , (1.187– 1.245) eV and (4.32 x1016–6.23 x1016 ) cm-3 , (1.374 -1.631)eV and (4.01 x1018 – 12.1 x1018 ) cm-3 respectively . The intensity of spectral lines, on the other hand, increased.

Utilizing laser spectrochemical analytical methods for assessing the ripening progress of tomato

To meet market demands and minimize losses, the tomato crop (Solanum Lycopersicum L.) requires a simple, rapid, and cost-effective method to distinguish between different maturity stages with high accuracy. This study aimed at evaluating two spectrochemical analytical techniques, namely laser-induced fluorescence (LIF) and laser-induced breakdown spectroscopy (LIBS), to discriminate three different maturity stages of tomato fruit (‘Green/Breaker’; ‘Turning/Pink’; and ‘Light-red/Red’). The simple linear regression confirmed the obtained LIF results with chlorophyll content (mg/100 g), hue angle (h°), and firmness (kg/cm2) of the different maturity stages (measured by conventional methods). Furthermore, the findings showed that the peak intensities of LIF spectra decreased with the chlorophyll content depletion during ripening. Moreover, the data exposed a reasonably good association between LIF spectra and chlorophyll content with a regression coefficient of 0.85. On the other hand, firmness and skin hue have shown an excellent predictor for the spectra with a high regression coefficient of 0.94. For LIBS spectra of each maturity stage, the ratios of Ca’s ionic-to-atomic spectral lines intensities have followed the same trend as conventionally measured firmness. The results demonstrated that LIF and LIBS are accurate, easy, and fast techniques used to define tomatoes’ different ripening stages. Both methods are useable in situ without any prior laboratory work.

The Temperature and Emission Measure Distribution in the Quiet and Active Solar Corona: A Bayesian Approach

The reconstruction of the differential emission measure (DEM) from observations of spectral line intensities provides information on the temperature distribution of the emission measure in the region observed. The inversion process is known to be highly unstable, and it has been necessary to provide additional constraints, such as requiring that the DEM should be smooth. However, this is a nonphysical constraint. The goal of this analysis is to make an empirical determination of the ability of a set of emission-line intensities to constrain the reconstruction. Here, a simple model is used, by means of a Markov Chain Monte Carlo process, to arrive at solutions that reproduce the observed intensities in a region of the quiet Sun and a solar active region. These solutions are compared by means of the reduced chi-squared. The conclusion from this analysis is that the observations are only capable of constraining a model consisting of four temperature–emission measure pairs plus a determination of the standard deviation of the model from the observed line intensities. A more complex model with five temperature–emission measure pairs does not improve the fit and leads to parameters that are irrelevant. A more general conclusion is that the information content of a set of observed emission lines is limited with respect to the determination of the emission measure distribution.

Online detection of laser paint removal based on laser-induced breakdown spectroscopy and the K-nearest neighbor method

Laser paint removal is a new highly efficient and environmentally friendly cleaning technology. Compared with traditional paint removal methods, laser paint removal is less labor intensive and can reduce environmental pollution. During laser paint removal, real-time monitoring is necessary to ensure efficient cleaning and process automation. Current methods for real-time monitoring of laser paint removal only determine whether the sample surface has been cleaned but provide no information on the status of any residual paint. In this article, spectral data of the sample surface have been obtained using laser-induced breakdown spectroscopy. It is shown that Zn and Fe spectral lines can be used in real time to characterize the effectiveness of paint removal and that the intensities of characteristic spectral lines are positively correlated with the single-pulse energy of the excitation light. The K-nearest neighbor algorithm was used to evaluate and automatically classify the extent of cleaning of sample surfaces in real time. When K = 3, the classification accuracy of distinguishing different levels of cleaning was 100%. The results of this study provide technical support for automatic and intelligent laser paint removal.

Characterization of the laser-induced breakdown spectroscopy near the gas-liquid two-phase interface.

The characterization of laser-induced breakdown spectroscopy (LIBS) near the gas-liquid two-phase interface was investigated with the laser acting on the sample along the horizontal direction. Simulation of the laser beam focusing process and observation of laser beam spot images show that difference in focusing positions in the air and the solution results from refraction of the laser beam entering the solution from the air and the change of propagation direction on the container lateral. The peak power and mean irradiance of the focused laser beam spot increase with the distance away from the interface, which is attributed to the fact that the loss of laser energy due to the refraction and reflection of light at the interface decreases with the focusing position moving away from the interface. This variation trend of laser irradiance allows for the growth of the spectral line intensity and lifetime with increasing the distance from the interface. The plasma electron density and temperature decrease with the delay time but increase with the distance away from the interface at the same delay time. Our findings help us to gain more insight into the characteristics and evolution mechanisms of LIBS produced near the gas-liquid two-phase interface, which provides theoretical guidance for the correction of LIBS spectra especially in water pollution monitoring.

Analysis of constituents present in smokeless tobacco (Nicotiana tabacum) using spectroscopic techniques

Laser-Induced Breakdown Spectroscopy (LIBS) is an analytical technique used to identify and quantify the elements present in any type of material present in any phase (solid, liquid, gas, and aerosol). In the present work, our objective is to find the presence of toxic and other elements in chewing tobacco ( Nicotiana tabacum ) using LIBS. Spectral signatures of elements like C, Fe, Si, Mg, Mn, Ca, Ti, Na, H, N, K, O, along with some toxic elements Al, Sr, Li, Cu, Sb, and Cr are observed in the LIBS spectra of these tobacco samples. The spectral intensity ratio is measured for quantitative analysis of elements present in the samples. Further, Atomic Absorption Spectroscopy is used for determining absolute concentration in these samples. A relation between the AAS result and the relative intensity of spectral lines measured in the LIBS is obtained using regression analysis. The multivariate technique, Principal Component Analysis (PCA), discriminates all the samples based on their toxicity and other constituents. Molecular study (Photoacoustic spectroscopy (PAS), UV-Visible (UV–vis), and FT-IR) of tobacco samples were performed to analyze the molecules present in the tobacco samples.

Detection of copper in solution by laser-induced breakdown spectroscopy based on nanoparticle chip

We report a highly sensitive electrolytic copper (Cu) detection method using nanoparticle enhanced laser-induced breakdown spectroscopy (NELIBS) for metal smelting processes. The sulfate solution Cu with content ranging from 10 to 50 g/L was prepared and measured on the nanoparticle chip. The experimental results showed that the Cu spectral line intensity of NELIBS increased 5.5 to 9.4 times compared with typical LIBS without nanoparticles. The calibration curve was established based on the spectral line intensity at Cu I 327.40 nm according to the different Cu content in the solution. The determination coefficient R2 of the calibration curve was 0.99. The method of laser-induced breakdown spectroscopy based on drying liquid droplets on the nanoparticle chip can be applied to the rapid determination of Cu content in the copper electrolyte.

Online in situ detection of local air conditions in hazardous operation scenarios

Although the risk of some hazardous operations has been greatly reduced, the changes in air conditions caused by them cannot be ignored. A lot of smoke is produced in some hazardous workplaces, which is very easy to cause air pollution. Exposed to this condition for a long time, human health is also greatly endangered. Therefore, the online detection of air conditions in hazardous workplaces is of great significance. In this work, electric welding operation is taken as an example to study the air conditions in hazardous workplaces. The real-time detection of smoke generated from electric welding operation is carried out by Laser induced breakdown spectroscopy (LIBS). The spectral line of lead is found in the smoke spectrum of lead tin wire. Some other metal elements are also detected in the smoke of the tin wire, such as Sn, Cu, Ca and K. Consequently, it is recommended to use lead-free tin wire. In addition, two welding scenarios are simulated. The results show that the generated smoke contains different element information with different welding objects. Then, the quantitative analysis of lead in smoke is carried out. It shows that the concentration of Pb can be calculated by the spectral line intensity in the spectrum. Finally, combined with the error back propagation artificial neural network (BP-ANN), different kinds of smoke are classified, and the recognition accuracy is more than 99%, which proves that the combination of LIBS and BP-ANN is developed into an important method in the monitoring of different air pollutants.

Determination of blood cholesterol concentration using calibration-based laser plasma spectroscopy and Fourier transform infrared technique

In this paper, the analysis of blood cholesterol is demonstrated using calibration curves derived from laser-induced breakdown spectroscopy (LIBS) and Fourier transform infrared (FTIR) technique. First of all, five standard samples and one target sample are prepared by adding different concentrations of cholesterol (as the analyte) to normal human blood serum (as the matrix). The plasma emission spectrum of the above samples is measured through LIBS process. Subsequently, considering the constituent elements of cholesterol (C27H46O), the relative average intensity of spectral lines having appropriate signal-to-noise ratio related to these elements is calculated. In the next step, four calibration curves of the relative average intensities are drawn in terms of cholesterol concentration of the samples. Finally, the target cholesterol concentration and its standard error of the mean (SEM) are obtained by the use of the calibration curves. In another way, cholesterol concentration of the target is also examined using the FTIR spectrum of the samples. Absorption bands corresponding to vibrational modes of the cholesterol molecule are identified. Then, the transmittance of the identified absorption peaks is plotted versus the blood cholesterol of the standard samples, and the cholesterol concentration of the target is determined by the resulted calibration lines. The results yielded from both LIBS and FTIR technique are in very good agreement with each other and with the certified value of the target cholesterol concentration, which once again indicates that in the molecular analysis, in addition to FTIR technique, LIBS method can also be very efficient.

Measurement and analysis of species distribution in laser-induced ablation plasma of an aluminum–magnesium alloy

We proposed a theoretical spatio-temporal imaging method, which was based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamics model. By using the intensity formula, the integral intensity of spectral lines could be calculated and the corresponding images of intensity distribution could be drawn. Through further image processing such as normalization, determination of minimum intensity, combination and color filtering, a relatively clear species distribution image in the plasma could be obtained. Using the above method, we simulated the plasma ablated from Al–Mg alloy by different laser energies under 1 atm argon, and obtained the theoretical spatio-temporal distributions of Mg I, Mg II, Al I, Al II and Ar I species, which are almost consistent with the experimental results by differential imaging. Compared with the experimental decay time constants, the consistency is higher at low laser energy, indicating that our theoretical model is more suitable for the plasma dominated by laser-supported combustion wave.

Solar Flare Irradiance: Observations and Physical Modeling

Abstract We examine Solar Dynamics Observatory (SDO)/EUV Variability Experiment (EVE) data to better understand solar flare irradiance, and how that irradiance may vary for large events. We measure scaling laws relating Geostationary Orbital Environmental Satellites (GOES) flare classes to irradiance in 21 lines measured with SDO/EVE, formed across a wide range of temperatures, and find that this scaling depends on the line-formation temperature. We extrapolate these irradiance values to large events, exceeding X10. In order to create full spectra, however, we need a physical model of the irradiance. We present the first results of a new physical model of solar flare irradiance, NRLFLARE, that sums together a series of flare loops to calculate the spectral irradiance ranging from the X-rays through the far-UV (≈0 to 1250 Å), constrained only by GOES/X-ray Sensors observations. We test this model against SDO/EVE data. The model spectra and time evolution compares well in high-temperature emission, but cooler lines show large discrepancies. We speculate that the discrepancies are likely due to both a nonuniform cross-section of the flaring loops as well as opacity effects. We then show that allowing the cross-sectional area to vary with height significantly improves agreement with observations, and is therefore a crucial parameter needed to accurately model the intensity of spectral lines, particularly in the transition region from 4.7 ≲ log T ≲ 6 .

Observation of Zeeman splitting effect in a laser-driven coil

The Zeeman splitting effect is observed in a strong magnetic field generated by a laser-driven coil. The expanding plasma from the coil wire surface is concentrated at the coil center and interacts with the simultaneously generated magnetic field. The Cu I spectral lines at wavelengths of 510.5541, 515.3235, and 521.8202 nm are detected and analyzed. The splittings of spectral lines are used to estimate the magnetic field strength at the coil center as ∼31.4 ± 15.7 T at a laser intensity of ∼5.6 × 1015 W/cm2, which agrees well with measurements using a B-dot probe. Some other plasma parameters of the central plasma disk are also studied. The temperature is evaluated from the Cu I spectral line intensity ratio, while the electron density is estimated from the Stark broadening effect.

«Atom» software for atomic spectral analysis

The capabilities of the Atom software used in the spectral analytical equipment manufactured by the VMK-Optoelektronika company are presented. Spectral measurements using various sources — inductively coupled plasma, microwave plasma, arc and spark discharge in air or argon atmosphere, atomic absorption, etc. — are discussed. Procedures allowing the traceability of measurement results are described. The calculation steps starting with calculation of the spectral line intensity to determination of the element content in the sample are briefly considered, as well as the estimation of statistical indicators and the metrological control of the measurement procedure according to GOST R ISO 5725. The advanced data export tools allow the transfer of results to external information systems, and, moreover, expand the functionality of the program through interaction with other applications. Various options for printing out using compact and extended presentations of results in the form of reports are available. The Atom software covers several methods of spectral analysis, including time-resolved spectrometry (scintillation, absorption, and analysis of non-metallic inclusions). Methods of qualitative and semi-quantitative analysis are offered in the form of separate additional tools. The Atom software distribution kit contains auxiliary information systems: a database of spectral lines, an alloy grade guide, a catalog of standard samples with certified elemental composition, and a database of the standard metrological characteristics of measurement methods. A distinctive feature of the Atom software is a well-thought-out user interface for the operation of any spectral-analytical equipment with high performance. The modern modular architecture of the program provides effective management of the project complexity and enables independent development of individual components using suitable tools.

A new atomic-emission spectrometer Grand-2000

The design of a Grand-2000 atomic emission spectrometer is considered. The optical efficiency and spectral resolution of a Grand-2000 spectrometer are compared with the corresponding characteristics of a Grand spectrometer with multi-element emission spectrum analyzers based on BLPP-2000 and BLPP-4000 photodetector arrays. The optical efficiencies are compared using the ratio of spectral line intensities recorded on the two spectrometers using the same types of photodetectors. The resolution of the spectrometers (FWHM of the spectral line) is measured using different types of photodetectors. It is shown that, when using BLPP-4000 photodetectors, the resolution of a Grand-2000 spectrometer is twice as large (4 pm), compared to a Grand spectrometer. The optical efficiency of a Grand-2000 spectrometer is 3 – 8 times lower, depending on the wavelength. It is also shown that a Grand-2000 spectrometer with BLPP-2000 photodetector arrays has better optical efficiency in the short-wavelength region compared to a Grand spectrometer with BLPP-4000 photodetector arrays at the same values of the spectral resolution.

Excitation of L-valine molecules by electrons and photons.

Excitation of L-valine molecules was studied by optical spectroscopy. Optical emission spectra of the L-valine molecule and optical excitation functions of molecular bands and the Hβ spectral line were measured in the gas phase using electron impact. In the spectra of optical emission in the wavelength range of 250–500 nm, intense emission bands were found at energies of incident electrons of 30, 50 and 70 eV. Analysis of structural features of the valine molecule suggested a fragmentation scheme with the formation of excited particles in collisions with electrons. A notable feature of the presented optical excitation functions is a different growth dynamics with an increase in the energy of exciting electrons and the presence of a number of features and kinks, which are especially pronounced for λ = 305 nm and λ = 311 nm. The excitation thresholds were determined from the initial sections of the excitation functions of the most intense spectral lines by the least-squares method. The photoluminescence spectra of L-valine were measured for the first time on a Shimadzu RF-6000 spectrofluorophotometer in the spectral range of 400–800 nm for excitation wavelengths of 250, 275, 333, 351, and 380 nm.Graphical abstract

Collisional-radiative recombination of Ne-=SUP=-++-=/SUP=- and Ne-=SUP=-+-=/SUP=- ions with electrons in the decaying plasma of a low-pressure barrier discharge

The results of an experimental study and simulation of radiation generated by the processes of collisional-radiative recombination of neon ions Ne+ and Ne++ with electrons of the decaying plasma are presented. Plasma was created by a barrier discharge in a cylindrical glass tube with electrodes on its surface. Experimental conditions: neon pressure 0.65 Torr, electron density at the initial stage of the afterglow [e] ~ (1-5)·1011 cm-3. The main attention is paid to the comparative analysis of the collisional-radiative recombination of Ne+ and Ne++ ions based on the numerical solution of coupled differential equations for the densities of charged and long-lived excited particles and the electron temperature, taking into account the main elementary processes in decaying neon plasma. Comparison of the model solutions with the intensities of ionic and atomic spectral lines measured by the multichannel photon counting method indicates the need to refine the dependence of the rate of collisional-radiative recombination on the ion charge. Keywords: dielectric barrier discharge, doubly charged ions, collisional-radiative recombination, decaying plasma, elementary processes.