A data selection method for matrix effects and uncertainty reduction for laser-induced breakdown spectroscopy

Severe matrix effects and high signal uncertainty are two key bottlenecks for the quantitative performance and wide applications of laser-induced breakdown spectroscopy(LIBS).Based on the understanding that the superposition of both matrix effects and signal uncertainty directly affects plasma parameters and further influences spectral intensity and LIBS quantification performance,a data selection method based on plasma temperature matching(DSPTM)was proposed to reduce both matrix effects and signal uncertainty.By selecting spectra with smaller plasma temperature differences for all samples,the proposed method was able to build up the quantification model to rely more on spectra with smaller matrix effects and signal uncertainty,therefore improving final quantification performance.When applied to quantitative analysis of the zinc content in brass alloys,it was found that both accuracy and precision were improved using either a univariate model or multiple linear regression(MLR).More specifically,for the univariate model,the root-mean-square error of prediction(RMSEP),the determination coefficients(R^(2))and relative standard derivation(RSD)were improved from 3.30%,0.864 and 18.8%to 1.06%,0.986 and 13.5%,respectively;while for MLR,RMSEP,R^(2)and RSD were improved from 3.22%,0.871 and 26.2%to 1.07%,0.986 and 17.4%,respectively.These results prove that DSPTM can be used as an effective method to reduce matrix effects and improve repeatability by selecting reliable data.

Matrix effect suppressing in the element analysis of soils by laser-induced breakdown spectroscopy with acoustic correction

Laser-induced breakdown spectroscopy(LIBS)has been used for soil analysis,but its measurement accuracy is often influenced by matrix effects of different kinds of soils.In this work,a method for matrix effect suppressing was developed using laser-induced plasma acoustic signals to correct the original spectrum,thereby improving the analysis accuracy of the soil elements.A good linear relationship was investigated firstly between the original spectral intensity and the acoustic signals.The relative standard deviations(RSDs)of Mg,Ca,Sr,and Ba elements were then calculated for both the original spectrum and the spectrum with the acoustic correction,and the RSDs were significantly reduced with the acoustic correction.Finally,calibration curves of MgⅠ285.213 nm,CaⅠ422.673 nm,SrⅠ460.733 nm and BaⅡ455.403 nm were established to assess the analytical performance of the proposed acoustic correction method.The values of the determination coefficient(R~2)of the calibration curves for Mg,Ca,Sr,and Ba elements,corrected by the acoustic amplitude,are improved from 0.9845,0.9588,0.6165,and 0.6490 to 0.9876,0.9677,0.8768,and 0.8209,respectively.The values of R~2 of the calibration curves corrected by the acoustic energy are further improved to 0.9917,0.9827,0.8835,and 0.8694,respectively.These results suggest that the matrix effect of LIBS on soils can be clearly improved by using acoustic correction,and acoustic energy correction works more efficiently than acoustic amplitude correction.This work provides a simple and efficient method for correcting matrix effects in the element analysis of soils by acoustic signals.

Mossbauer spectroscopy studies on the particle size distribution effect of Fe–B–P amorphous alloy on the microwave absorption properties

An Fe-based nanocrystalline alloy powder is important for application in microwave absorption,and the particle size has a critical impact on the electromagnetic microwave parameters.Therefore,it is necessary to study further the effects of the particle size on such parameters and improve the microwave absorption performance of Febased nanocrystalline powers.In this study,Fe-B-P particles were prepared through a synthetic approach consisting of an aqueous chemical reduction and a ball milling treatment.We investigated the effects of ball milling on the microstructure and electromagnetic properties of Fe-B-P particles.The experimental results indicate that the Fe-B-P particles synthesized through an aqueous chemical reduction are amorphous spheres.Fe-B-P particles with an original particle size of 200-1200 nm can be milled into an irregular shape with the size reduced to\500 nm after 0.5 h of ball milling,and subsequently,the particles become smaller with increases in the milling time,with traces of Fe2O3 generated on the particle surface.The results of the Mo¨ssbauer spectra show that a portion of the small particles demonstrate a superparamagnetic property.The volume proportions of the superparamagnetic component increase from 13.1 to 15.8%as the treatment time increases.We measured the permittivity and permeability spectra of Fe-B-P particles within the frequency range of 2-18 GHz.The reflection loss(RL)is-10 dB for an absorber thickness of 1.7-5.0 mm.The RL is-20 dB for an absorber thickness of 1.9-2.7 mm.The microwave absorption properties of samples with the same thickness are improved with an increase in the treatment time and are shifted to a higher frequency,which will broaden the bandwidth of the absorption as well.

Electron Momentum Spectroscopy of Valence Orbitals of n-Propyl Iodide： Spin-Orbit Coupling Effect and Intramolecular Orbital Interaction

The binding energy spectrum and electron momentum distributions for the outer valence orbitals of n-propyl iodide molecule have been measured using the electron momentum spectrometer employing non-coplanar asymmetric geometry at impact energy of 2.5 keV plus binding energy. The ionization bands have been assigned in detail via the high accuracy SACCI general-R method calculation and the experimental momentum profiles are compared with the theoretical ones calculated by Hartree-Fock and B3LYP/aug-cc-pVTZ（C,H）6-311G？？（I）. The spin-orbit coupling effect and intramolecular orbital interaction have been analyzed for the outermost two bands, which are assigned to the iodine 5p lone pairs, using NBO method and non-relativistic as well as relativistic calculations. It is found that both of the interactions will lead to the observed differences in electron momentum distributions. The experimental results agree with the relativistic theoretical momentum profiles, indicating that the spin-orbit coupling effect dominates in n-propyl iodide molecule.

Study of pressure effects on ocean in-situ detection using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy(LIBS) has attracted extensive attention as a new technique for in-situ marine application. In this work, the influence of deep-sea high pressure environment on LIBS signals was investigated by using a compact LIBS-sea system developed by Ocean University of China for the in-situ chemical analysis of seawater. The results from the field measurements show that the liquid pressure has a significant effect on the LIBS signals. Higher peak intensity and larger line broadening were obtained as the pressure increases. By comparing the variations of the temperature and salinity with the LIBS signals, a weak correlation between them can be observed. Under high pressure conditions, the optimal laser energy was higher than that in air environment. When the laser energy exceeded 17 mJ, the effect of laser energy on the signal intensity weakened. The signal intensity decreases gradually at larger delays. The obtained results verified the feasibility of the LIBS technique for the deep-sea in-situ detection, and we hope this technology can contribute to surveying more deep-sea environments such as the hydrothermal vent regions.

Research on Kaolinite in Coal Measures of West Beijing by Mossbauer Spectroscopy

The spatial occurrence of iron in kaolinite of coal measures west of Beijing was studied by using the Mossbauer spectroscopy technique and a step-by-step method of fitting. The results show that there are three kinds of spatial occurrence in kaolinites： tetra-coordination Fe（3＋） in Si-O tetrahedrons, sexa-coordination Fe（3＋） in A1--O octahedrons and sexa-coordination Fe（2＋） in A1-O octahedrons, respectively occupying 51.72 %, 37.25 % and 11.03 %, Neither foreign matter of magnetic Fe mineral nor superparamagnetic goethite exists in kaolin concentrates. Fe in kaolin concentrates cannot be removed by conventional methods, which is significant for both theoretical research on kaolinite minerology and practical use of the kaolinites of coal measures west of Beijing.The research also illustrates that the Mossbauer spectroscopy is an effective method in studying the micro-superfine Fe in kaolin.

Effect of parameter setting and spectral normalization approach on study of matrix effect by laser induced breakdown spectroscopy of Ag–Zn binary composites

The complex nature of laser-material interaction causes non-stoichiometric ablation of alloy samples.This is attributed to matrix effect, which reduces analyzing capability. To address this issue, the analytical performance of three different normalization methods, namely normalization with background, internal normalization and three point smoothing techniques at different parameter settings is studied for quantification of Ag and Zn by Laser induced breakdown spectroscopy(LIBS).The LIBS spectra of five known concentration of silver zinc binary composites have been investigated at various laser irradiances(LIs). Calibration curves for both Ag(I) line(4d^(10)5s^2S_(1/2)→4d^(10)5p^2P_(1/2) at 338.28 nm) and Zn(I) line(4s5s^3S_1→4s4p^3P_2 at 481.053 nm) have been determined at LI of 5.86?×?10^(10)W cm^(-2). Slopes of these calibration curves provide the valuation of matrix effect in the Ag–Zn composites. With careful sample preparation and normalization after smoothing at optimum parameter setting(OPS), the minimization of sample matrix effect has been successfully achieved. A good linearity has been obtained in Ag and Zn calibration curve at OPS when normalized the whole area of spectrum after smoothing and the obtained coefficients of determination values were R^2?=?0.995 and 0.998 closer to 1. The results of matrix effect have been further verified by analysis of plasma parameters. Both plasma parameters showed no change with varying concentration at OPS. However, at high concentration of Ag, the observed significant changes in both plasma parameters at common parameter setting PS-1 and PS-2 were the gesture of matrix effect. In our case, the better analytical results were obtained at smoothing function with optimized parameter setting that indicates it is more efficient than normalization with background and internal normalization method.

Unraveling Shuttle Effect and Suppression Strategy in Lithium/Sulfur Cells by In Situ/Operando X-ray Absorption Spectroscopic Characterization

The polysulfides shuttle effect represents a great challenge in achieving high capacity and long lifespan of lithium/sulfur(Li/S)cells.A comprehensive understanding of the shuttle-related sulfur speciation and diffusion process is vital for addressing this issue.Herein,we employed in situ/operando X-ray absorption spectroscopy(XAS)to trace the migration of polysulfides across the Li/S cells by precisely monitoring the sulfur chemical speciation at the cathodic electrolyte-separator and electrolyte-anode interfaces,respectively,in a real-time condition.After we adopted a shuttle-suppressing strategy by introducing an electrocatalytic layer of twinborn bismuth sulfide/bismuth oxide nanoclusters in a carbon matrix(BSOC),we found the Li/S cell showed greatly improved sulfur utilization and longer life span.The operando S Kedge XAS results revealed that the BSOC modification was bi-functional:trapping polysulfides and catalyzing conversion of sulfur species simultaneously.We elucidated that the polysulfide trapping-and-catalyzing effect of the BSOC electrocatalytic layer resulted in an effective lithium anode protection.Our results could offer potential stratagem for designing more advanced Li/S cells.

Doping Copper Ions in a Metal-Organic Framework(UiO-66-NH2):Location Effect Examined by Ultrafast Spectroscopy

We constructed two types of copper-doped metal-organic framework(MOF),i.e.,Cu@UiO-66-NH2 and Cu-UiO-66-NH2.In the former,Cu2+ions are impregnated in the pore space of the amine-functionalized,Zr-based UiO-66-NH2;while in the latter,Cu^2+ions are incorporated to form a bimetal-center MOF,with Zr^4+being partially replaced by Cu2+in the Zr-O oxo-clusters.Ultrafast spectroscopy revealed that the photoinduced relaxation kinetics associated with the ligand-to-cluster charge-transfer state is promoted for both Cudoped MOFs relative to undoped one,but in a sequence of Cu-UiO-66-NH2>Cu@UiO-66-NH2>UiO-66-NH2.Such a sequence turned to be in line with the trend observed in the visible-light photocatalytic hydrogen evolution activity tests on the three MOFs.These findings highlighted the subtle effect of copper-doping location in this Zr-based MOF system,further suggesting that rational engineering of the specific metal-doping location in alike MOF systems to promote the photoinduced charge separation and hence suppress the detrimental charge recombination therein is beneficial for achieving improved performances in MOF-based photocatalysis.

A MOSSBAUER EFFECT STUDY ON Co DOPING IN SmTiFe_(11) COMPOUND

A series of SmTiFe11-xCox compounds where x ranges from zero to five, have been studied by Fe Mossbauer spectroscopy, X-ray diffraction and related magnetic measurements. The radom site occupation of Co atom in SmTiFe11-xCox was found when x≥1. The temperature dependence of the magnetic hyperfine field for SmTiFe11 and the Co concentration dependence of the magnetic hyperfine field for the samples, SmTiFe11-xCox are obtained. Also the Debye temperature of SmTiFe11 have been estimated from the experiments.

MOSSBAUER SPECTROSCOPIC STUDY OF FIRED SHENQIU METEORITES

The Shenqiu meteorite was investigated by Mossbauer spectroscopy at room temperature, atomic absorption, X-ray diffraction and scanning electron microscopy. In order to determine fired conditions of the meteorite which occurred during the meteorite fall, Shenqiu meteorite samples were fired in an oxidizing atmosphere and a reducing atmosphere at temperatures up to 1300℃, respectively. These samples also were fired at 800, 1000 and 1200 ℃ respectively for different time (up to 24 h).

TRACKING PYRITIC SULFUR DURING THE MICROWAVE- CHEMICAL DESULFURIZATION OF COAL USING MOSSBAUER SPECTROSCOPY

The transformations of pyrite in coal during the microwave-chemical treatment for desulfurization of coal was studied with Mossbauer spectroscopy of Fe. The results for phase analyses show that the selective dielectric heating by microwave energy can give rise to the thermal decomposition of pyrite FeS2 in coal to new phases, pyrrhotite Fe1-xS (0【x≤0.125) and troilite FeS which can be dissolved in dilute HC1 solution. Therefore the microwave irradiation combined with the acid washing treatment will be an effective method of desulfurization of coal.

ITALIAN MONEY TESTED FOR FORGERY BY MOSSBAUER SPECTROSCOPY

Italian money has been investigated by Mossbauer spectroscopy. The results indicated that the spectrum of a 10000 lire bank-note consisted of three magnetic sextets and two quadrupole doublets, the spectrum of a 50000 lire note consisted of two Zeeman sextets, but in the "false" money there are two quadrupole doublets only.

MOSSBAUER POLARIMETER AND MOSSBAUER FARADAY EFFECT

A Mossbauer polarimeter consists of a gamma ray source (polarizer), transmitter (sample to be analyzed), analyzer and automatic counting system. This equipment was used to observe the Mossbauer Faraday effect in non-stoichiometric Fe3O4. Experimental results demonstrated that electronic hopping above the Verwey temperature between Fe2+- Fe3+ ions on the octahedral sites is a only localized phenomenon and the recoilless fractions of 57Fe nuclei in Fe3-vO4 (v=0.02) are 0.71 for A sites and 0.62 for B sites, respectively.

Mossbauer Effect of Rapidly Quenched Al-Fe-V-Si-Mm Alloys

The iron atomic location in Al(93.3-x)Fe(4.3)V(0.7)Si(1.7)Mm(x)(x=0, 1, 3, 6) alloys was investigated by means of Mossbauer spectroscopy and X-ray diffraction. The results show that the appearance of bcc a-Al-13(Fe, V)(3)Si dispersive particles existing in Al-Fe-V-Si alloy is suppressed by:the addition of misch metal, A new Al-Fe-V-Si-Mm amorphous alloy is formed when the concentration of misch metal is up to 6 at%, in the meantime, the corresponding structural analysis is made using Voigt-based fitting method.

PROGRESS IN MOSSBAUER SPECTROSCOPY

Mossbauer effect, a nuclear analogue of resonance fluorescence, has proven to be one of the most effective experimental methods for the scientific investigation in a large variety of problems from nuclear physics to medicine. The popularity of the method ia due to the fact that it allows one to carry out experiments with the highest energy resolution. Approximately 1000 articles have been published during each of the last 10 years. In this review, we will discuss some of recent developments in this field, the applications in natural science, and some industrial applications. Finally, the general conditions of Mbssbauer spectroscopy will be discussed and the present situation of this field in China will be involved.

Dielectric behaviors at microwave frequencies and Mossbauer effects of chalcedony, agate, and zultanite

In this study, dielectric properties within 8-12 GHz microwave frequencies, inductively coupled plasma-atomic emis- sion spectrometry, Fourier transform infrared spectrometry, synchronized two thermal analyses, and 57Fe Mossbauer spectroscopy analysis of chalcedony, agate, and zultanite samples from Turkey are presented. Agate and chalcedony show the same nine vibrational absorption peaks obtained unlike zultanite from FTIR spectra in the 350 cm-1 to 4000 cm-1 range, ε＇ values of chalcedony, agate and zultanite derived at 10.5 GHz were 4.67, 4.41, and 7.34, respectively, eI and e~ values of the studied samples at the microwave frequencies are related to the percentage weight of their constituent parts in their chemical compositions. 57Fe Mossbauer spectroscopy results confirm the existence of iron-containing islands in the crystal structure of zultanite, agate, and chalcedony samples, equipped them with magnetic features typical for magnetic nanoparticles including superparamagnetism. The presence of iron-containing islands significantly affects the magnetic, dielectric, and optical properties of studied samples that are not observed for pure minerals without any foreign inclusions.

^(199)Sn AND ^(57)Fe MOSSBAUER SPECTROSCOPIC STUDY OF THE MECHANICALLY ALLOYED Fe-Sn ALLOYS

Nanocrystalline supersaturated solid solutions (Sa in Fe) with Sn content less than 50 at. %,and FeSn2 and Fe1.3Sn intermetallic compounds have been prepared by mechanical alloying of Fe and Sn mixture powders with composition of Fe1-xSnx (x≤0.5).The atomic alloying the formation and microstructure, especially the coordination environments, of the resultant alloys have been studied by X-ray diffraction, 57Fe and 119Sn Mossbauer Spectroscopy and diffrrential scanning calorimetry. The Fe and Sn coordination environments and the composition dependence of the hyperfine parameters on the Fe and Sn content have been fully discussed with respect to the solid dissolution alloying, grain refinement, and distortion caused or induced by mechanical alloying.

An Exact Expression for Fractional Absorption in Mossbauer Spectroscopy

The fractional resonance absorption ε(0) in transmission Mossbauer spectroscopy is defined as a relative number of the absorbed γ-ray, and regarded as a measure of Mossbauer effect. The absorption linewidth Λ a , as it is usually suggested, is nearly equal to the emission linewidth, Λ s , and such an approximation leads to a extremely simplified expression ε(0), depending on neither Λ s nor Λ a . We consider the general case Λ s ≠Λ a , and obtain an exact expression for ε(0) which is given in the present paper. This expression ε(0), as a function oft a, Λ s , Λ a , is figured and discussed.

MOSSBAUER SPECTROSCOPY OF HIGH T_c YBa_2 (Cu_(3-x)Fe_x )O_y

YBa2(Cu3-xFex)Oy (x is 0.001, 0.005, 0.01, 0.1 and 0.3 respectively), of whichCu is replaced with 57Fe are studied using M0ssbauer spectroscopy to understand thecrystal lattice property, the effects of the replacement on superconductivity of theHigh To materials.