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CaOH Molecular Emissions in Underwater Laser-Induced Breakdown Spectroscopy: Spatial–Temporal Characteristics and Analytical Performances
摘要： Recently, molecular emissions from the laser-induced plasma in ambient gas have gained increasing interest; however, very little is known about the case in water solutions. In this work, we investigated the spatiotemporal characteristics of molecular emissions, CaOH for instance, in underwater laser-induced breakdown spectroscopy (LIBS) by using time-resolved spectroscopy, spectral-resolved imaging, and shadowgraph techniques. It was shown that clear CaOH molecular bands can be observed in the spectrum at very early times after the laser pulse and presented a much longer lifetime and more homogeneous emission distribution compared with the Ca I and Ca II lines. Such unique characteristics of CaOH molecular emission inspired us to improve the performances of underwater LIBS by using the CaOH molecular bands instead of Ca I and Ca II lines. We demonstrated the excellent quanti?cation results of CaOH with higher stability, less self-absorption, and reduced matrix e?ect. Meanwhile, the limit of detection (LOD) of Ca with the CaOH molecular band (2.46 ppm) is comparable to that with the atomic line of Ca I (2.07 ppm), and much lower than that with the ionic line of Ca II (13.81 ppm), indicating a good sensitivity of CaOH. This work gives not only some insights into the molecule formation mechanisms in underwater plasmas, but also provides new ideas to improve the analytical performances of underwater LIBS.
关键词： analytical performances,CaOH molecular emissions,underwater laser-induced breakdown spectroscopy,spatiotemporal characteristics
更新于2025-09-19 17:13:59
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Plasma Diagnostic by Optical Emission Spectroscopy on Dolomite and Cross-Validation Using Scanning Electron Microscopy Coupled with Energy Dispersive X-ray Spectroscopy and Electron Probe Micro-Analysis
摘要： Dolomite [CaMg(CO3)2] is an important carbonate mineral mainly composed of calcium magnesium carbonate. The correct determination of magnesium content in carbonate rocks is important for accessing its suitability for different applications; however, presence of different phases with varying magnesium contents makes their analysis difficult. In the present work, a natural carbonate mineral dolomite is analyzed qualitatively and quantitatively using laser-induced breakdown spectroscopy along with X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and electron-probe microanalysis. The optical emission spectra recorded in 200–720 nm wavelength region revealed presence of emission lines for Ca, Mg, Al, Sr, and Na with varying intensities. We used two different techniques, that is, Boltzmann plot and Saha–Boltzmann plot methods to calculate the plasma temperature, and an average value of 4500 ± 450 K was deduced.The Stark broadening line profile method was exploited to calculate the electron number density using calcium and magnesium lines which resulted in 2.39 × 1017 cm–3. The quantitative compositional analysis was carried out using calibration-free laser-induced breakdown spectroscopy method for which the local thermodynamic equilibrium and optically thin plasma conditions were satisfied.The composition for dolomite major constituents calcium and magnesium were estimated as 68.58 and 31.41%, respectively.The results demonstrated the LIBS, EDS, and EPMA ability as an effective, powerful and complementary analytical techniques for the elemental composition analysis of carbonate minerals.
关键词： magnesium,calibration-free laser-induced breakdown spectroscopy,EPMA,plasma diagnostic techniques,dolomite,EDS
更新于2025-09-19 17:13:59
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Improvement of classification accuracy of stainless steel alloys by laser-induced breakdown spectroscopy based on elemental intensity ratio analysis
摘要： Laser-induced breakdown spectroscopy (LIBS) is a useful technique for accurate sorting of metal scraps by chemical composition analysis. In this work, a method for intensity-ratio-based LIBS classification of stainless steel applicable to highly fluctuating LIBS signal conditions is proposed. The spectral line pairs for intensity ratio calculation were selected on the consideration of elemental concentration and upper levels of emission lines. It is demonstrated that the classification accuracy can be significantly improved from that of full spectra principal component analysis or intensity-based analysis. The proposed method is considered to be suited for an industrial scrap sorting system that requires minimal maintenance and low system price.
关键词： intensity ratio,laser-induced breakdown spectroscopy (LIBS),stainless steel,classification
更新于2025-09-19 17:13:59
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Revealing the impact of laser-induced breakdown on a gas flow
摘要： Laser-induced breakdown spectroscopy (LIBS) is an optical, and thus non-contact, but not non-invasive, measurement technique. Investigating the impact of laser-induced breakdown on a gas flow, combined LIBS and particle image velocimetry (PIV) measurements are performed. In the considered laminar air flow, the induced velocity field disturbance has an extent of about 0.7 cm with magnitudes up to 0.9 m s?1. As a further result, the combination of LIBS with other measurement techniques or high-speed LIBS measurements are found to require a minimal time delay of about 500 μs in order to ensure influence of the preceding LIBS pulse on the considered gas flow of about 10 % relative velocity deviation. For a reduction to 0 % relative velocity deviation a time delay of about 20 ms is estimated for the investigated flow. Smaller time delays may occur in turbulent flows or flows with higher velocities.
关键词： laser-induced breakdown spectroscopy,Flow diagnostics,particle image velocimetry
更新于2025-09-19 17:13:59
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Improving the Detection Sensitivity for Laser-Induced Breakdown Spectroscopy: A Review
摘要： Laser-induced breakdown spectroscopy (LIBS) is fast, on-line, causes little sample damage, and can be applied in remote field locations. In recent years, LIBS has been widely used in many fields of scientific research for element detection. Further application of LIBS is limited by the strong matrix effect, poor repeatability, and relatively weak detection sensitivity. The detection sensitivity is an important factor and needs to be improved for LIBS detection of minor or trace elements in samples. A variety of methods have been developed to improve detection sensitivity of LIBS. In this invited review paper, we discuss improvements in the LIBS detection sensitivity achieved with physical enhancement methods, chemical enhancement methods, mathematical methods, and combinations of multiple methods. We discuss the enhancement mechanisms, sensitivity improvements, configurations, and effects of key factors for various methods. The advantages, disadvantages, and real-time capabilities of these methods are reviewed. Finally, new trends and future perspectives for LIBS as an efficient analytical tool are discussed.
关键词： mathematical method,physical enhancement,laser-induced breakdown spectroscopy,chemical enhancement,detection sensitivity
更新于2025-09-19 17:13:59
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EXPRESS: Signal Enhancement Evaluation of Laser Induced Breakdown Spectroscopy of Extracted Animal Fats Using a Principal Component Analysis Approach
摘要： In this work, principal component analysis (PCA) was utilized to analyze laser-induced breakdown spectroscopy (LIBS) signals of extracted chicken fat, lamb fat, beef fat, and lard froze using two different freezing methods. The frozen samples were ablated using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser with a wavelength of 1064 nm, 170 mJ pulse energy, and 6 ns pulse duration to produce plasma on target surfaces. The samples were ablated using 30–60 shots of the laser beam at different spots. Stronger LIBS signals from extracted chicken fat and lamb fat were obtained with liquid nitrogen (LN2) method. However, LIBS signals obtained from the freezer freezing method were found to be stronger for extracted beef fat and lard. The PCA was then used to visualize the LIBS spectra of extracted animal fats into a score plot. Data points of each extracted animal fat were divided into three groups representing LIBS spectra collected at the early, middle and end part of the ablation process. The score plot revealed that the data points of the three groups of frozen extracted animal fats using the LN2 method were more closely clustered than those frozen in the freezer. Good discrimination with 97% of the variance was achieved between extracted the chicken fat, lamb fat, beef fat ,and lard using the LN2 method in the 3D score plot. LIBS signals of extracted animal fats produced from the LN2 method were found to be more stable than those from the freezer method.
关键词： Laser induced breakdown spectroscopy,LIBS,PCA,principal component analysis,liquid,animal fat,plasma
更新于2025-09-19 17:13:59
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Temporal Evolution of Polarization Resolved Laser-Induced Breakdown Spectroscopy of Cu
摘要： Polarization-resolved laser-induced breakdown spectroscopy based on a temporal investigation of polarized Cu plasma emission is presented by a gated detector with a width of 10 ns and a delay time range of 10 ns–2 μs. Polarization-resolved spectra show that the delay time plays a crucial role in plasma polarization for both continuum and discrete emissions. The polarization degree of continuum emission is shown to be stronger than the polarization degree of discrete emissions at delay times less than 500 ns, while this trend is inverse in a delay time range of 750 ns–1 μs. The mechanism for polarized continuum emission is proposed to have dynamic polarizability of a core, while the polarized discrete emission is driven by the interaction of the plasma with the surrounding environment. The latter may lead either to a deviation of plasma from local thermodynamic equilibrium or generation of self-magnetic fields.
关键词： Polarization-resolved laser-induced breakdown spectroscopy,Polarization,Laser-induced breakdown spectroscopy,Local temperature equilibrium,Self-generated magnetic field
更新于2025-09-16 10:30:52
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Multivariate determination of 10B isotopic ratio by laser-induced breakdown spectroscopy using multiple BO molecular emissions
摘要： Measurements of boron isotopic ratios have been investigated using LIBS, and combined LIBS and Molecular laser-induced fluorescence (MLIF). Mixtures of various ratios of research grade H3 11BO3 and H3 10BO3 in pellet form were interrogated with a Q-switched Nd:YAG laser operating at 532 nm. The resulting plasma was examined for their BO molecular bands in the 254–262 nm and 266–276 nm wavelength ranges. A minimum of three band heads of the β system B2Σ → X2Σ transitions were identified. The rovibronic isotopic shifts of the corresponding bands were measured and were conclusively compared to the literature. MLIF was applied to LIBS emission lines covering 253–271 nm to enhance some band heads, selectively. Both LIBS and LIBS-MLIF emissions were subject to multivariate statistical analysis to predict 10B isotopic ratios. Two PLS regression calibration models were examined to better examine the effects, sensitivity, accuracy of the laser-produced plasma excitation modalities based models through the figure of merit. For the full calibration set (21 samples), the root mean square error of cross-validation (RMSECV), the pseudo univariate LOD (LODpu) and the LOD interval ([LODmin, LODmax]) for 10B isotopes were improved from 1.61%, 4.81%, [2.64%, 3.49%] 10B isotopic ratio, respectively for LIBS to 0.98%, 2.40%, [2.19%, 2.81%] 10B isotopic ratio, respectively for LIBS-MLIF. However, using a random subset of the samples (14) as a calibration set and the rest as a test set, the root mean square error of prediction of 10B isotopic ratio in the test set improved from 2.95% to 1.16% 10B isotopic ratio, respectively for LIBS and LIBS-MLIF; and the LOD interval improved from [2.45%, 2.69%] to [1.88%, 2.12%] 10B isotopic ratio when calculated with cross-validated residual variance. Moreover, the prediction error of a test set improved from 2.95% for LIBS to 1.16% for LIBS-MLIF.
关键词： Molecular laser-induced fluorescence,LIBS-MLIF,Limit of detection interval,Laser-induced breakdown spectroscopy,Boron isotopes,Molecular band
更新于2025-09-16 10:30:52
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Influence of laser wavelength on self-absorption effect in laser-induced breakdown spectroscopy
摘要： Self-absorption effect seriously affects the accuracy of the quantitative analysis in laser-induced breakdown spectroscopy (LIBS), confining the further development of the technology. In this study, three laser wavelengths at ultraviolet (355 nm), visible light (532 nm), and infrared (1064 nm) were selected to study the influence of laser wavelength on self-absorption effect in LIBS. The effect of the laser wavelength the on spectral stability was also investigated. The results showed that when the wavelength was 1064 nm compared with the wavelength of 355 nm and 532 nm, the full widths at half maximum (FWHMs) of aluminum (Al) I 396.2 nm were reduced by 39% and 23%, the FWHM of potassium (K) I 766.5 nm were reduced by 58% and 22%. In addition, the laser wavelength was also closely related to the stability of the spectral intensity. In comparison with the laser wavelengths of 532 nm and 1064 nm, the best spectral repeatability occurred when the laser wavelength was 355 nm. The relative standard deviation (RSD) of the K I 766.5 nm was only 2.5%. The results indicate that laser wavelength affects the self-absorption effect and spectral stability of LIBS, which means selecting an appropriate laser wavelength can reduce self-absorption and improve stability.
关键词： Laser-induced Breakdown Spectroscopy,Self-absorption,Laser wavelength,Relative standard deviation
更新于2025-09-16 10:30:52
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Detection of heavy metal containment of soil pollution due to waste of paper industry using Nd:YAG laser induced breakdown spectroscopy
摘要： Detection of heavy metal containment of soil pollution has been made by using laser-induced breakdown spectroscopy (LIBS). A pulsed Nd:YAG laser (1064 nm, 8 ns, 200 mJ) was focused on to a soil sample, which is prepared in the form of pellet, at atmospheric pressure. Emission spectra taken from the waste-contaminated soil and uncontaminated soil were obtained. Plasma emissions are then detected using a multichannel analyzer (OMA) to obtain the emission line spectrum that represents the content of atoms and molecules in the target material. The spectrum is recorded and compared with the spectrum of reference standards of atoms, ions and molecules (National Institute of Standards and Technology/NIST) so that the atomic and molecular content in the sample can be known. From the results of the study it was found that there are elements of heavy metals in the form of Fe, Cd, and Mg in polluted soils.
关键词： LIBS,laser-induced breakdown spectroscopy,soil pollution,heavy metal,Nd:YAG laser
更新于2025-09-16 10:30:52