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This paper presents a self-consistent multi-dimensional mathematical model and a numerical approach for simulating the low-temperature plasma induced by the femtosecond laser filament. Addressing limitations in current models, we analyze key aspects of the laser plasma behavior, including plasma generation, detailed chemical kinetics, energy exchange channels, total energy balance, and hydrodynamics. The developed model and LOTASFOAM code are applied to study the temporal and spatial decay of the plasma produced by a femtosecond laser pulse in pure nitrogen at atmospheric pressure. The paper also includes a discussion on the spatial and temporal dynamics of electronically excited states of nitrogen in the decaying laser plasma. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS), a rapid and nondestructive elemental analysis method, is widely applied across various fields. This technique is used for elemental analysis of materials by analyzing the light emitted from laser-induced plasma, with plasma temperature being a crucial parameter. This study focused on obtaining time-resolved spectra of Cu samples at different distances from the lens to the sample using LIBS in conjunction with the following machine-learning algorithms to simulate plasma temperature: decision trees, support vector machine, Gaussian process regression, and neural network. The study compared the accuracy of these four algorithms before and after normalization based on the Cu (I) spectral line at 510.55 nm. All four algorithms achieved a correlation coefficient greater than 0.95 after normalization. The Gaussian process regression model provided excellent predictions before and after normalization with a correlation coefficient of 0.99, demonstrating the advantages of this model in plasma temperature simulation. This study confirmed that machine learning can effectively, conveniently, and accurately predict laser-induced plasma temperature, providing significant utility in LIBS research. [ABSTRACT FROM AUTHOR]

An experimental study on the packing thickness (PT) dependent plasma emission caused by laser ablating thin-layer microgranular samples in air was conducted using three sets of size-selected copper grains (median size d50 = 53 mm, 72 mm, and 100 mm, respectively). For each size-selected case, the PT parameter was tuned from 0.15 to 1.00 mm through varying the amount of grains packed into a vessel with a steel bottom wall and the emission spectra of laser-induced plasma were measured at various PT. It is found that there is a striking threshold phenomenon in the measured behavior of PTdependent plasma emission. Specifically, when PT is less than a threshold PTth, the emission intensity exhibits an exponential decreasing with incremental thickness; however, when it exceeds PTth, the emission intensity becomes almost constant. It is also found that the PTth slightly depends on grain size but the ratio of PTth to d50 seems to be size independent. Combining the mechanical fundamentals of granular materials, we interpreted the findings by considering a PT-dependent effect of the vessel's bottom on the formation circumstance of a laser-induced plasma. This work has practical significance in assessing a threshold thickness above which laser-induced breakdown spectroscopy, as an analytical technique to quantify elements embedded in microgranular materials, is viable regardless of PT difference. [ABSTRACT FROM AUTHOR]

The present study describes the potential use of the Laser-induced breakdown spectroscopy (LIBS) coupled with the principle component analysis (PCA) for the discrimination/analysis of the precious gold alloy has been reported. It is very hard to discriminate between the Au-Alloys using conventional LIBS and it has been suggested that the use of multivariate methods assisted LIBS could solve the problem. Gold alloys of karats 18 K, 19 K, 20 K, 22 K, and 24 K with concentrations of 75, 79, 85, 93, and 99.9% have been tested and analyzed using LIBS. Plasma was generated on the surface of the target sample by focusing Nd: YAG laser under atmospheric pressure. Time-integrated emission spectra from plasma were collected in the range of 250–870 nm. The characteristic emission lines of constituents were identified using the NIST atomic spectra database. Normalized optical emission intensities of the detected elements were used as input data for principle component analysis (PCA). Five different three-dimensional clusters were observed, that belonged to five different karats of gold, suggesting the reliability of the model for the classification of precious alloy samples. The finding from this study showed that the LIBS coupled with PCA is an effective method for the classification of gold alloys with different percentages. [ABSTRACT FROM AUTHOR]

This study aims to analyze the spectral properties of plasma produced from rice husk(Rh) using the laser breakdown spectroscopy (LIBS) method. The plasma generation process used the fundamental harmonic (1064 nm) of a Q-switched Nd:YAG laser. Yttrium aluminum garnet (YAG) is a man-made crystalline material. The laser fired pulses with a duration of 10 ns and a repetition rate of 6 Hz. Thus, the energy outputs achieved were 50–200 mJ at the wavelength of 1064 (nm). The silica content in the rice hulls was verified using an XRF measurement, which revealed the presence of silica in the rice hulls in a high percentage. Precise beam focusing was achieved by focusing the laser on the target material. This target material is placed within an atmospheric environment at standard pressure settings. The electron temperature was derived using the Boltzmann diagram method by harnessing experimental data for the linear properties associated with the neutral lines (Si II), (O II), and ion lines (Si I). The use of analytical methodology led to the determination of electron temperature values from 0.79 eV to 1.16 eV for the fundamental harmonic of the laser. At the same time, the electron (ne) density was determined by analyzing the Stark broadening profile associated with the neutral silica line. Furthermore, the study included an additional dimension by determining the plasma properties (electron temperature and electron density) by adjusting the laser energy on the target surface longitudinally along the path of the plasma plume. [ABSTRACT FROM AUTHOR]

The impact of oxidation chemistry on the emission characteristics and spatial structure of laser-produced Ce metal plasmas was investigated using laser-induced breakdown spectroscopy (LIBS) and time-resolved fast-gated imaging employing narrowband optical filters. Images of the plasma emission show that CeO coexists with atomic species in the periphery and vortex ring of the plasma plume. Image processing was also applied to combine independent monochromatic images of the plasma emission into a single merged image, culminating in a timelapse on the spatiotemporal evolution of atomic and molecular species within the plasma plume. The formation of CeO species was observed to proceed faster for plasmas generated in atmospheres containing larger concentrations of oxygen based on ratios of CeO-to-atomic emission intensities. These same ratios were shown to plateau and decrease at later times (≥25 μs), potentially indicating the depletion of CeO number densities in the plasma as the monoxide undergoes reactions to form higher polyatomic oxides. Altogether, these results provide fundamental insights into the chemical dynamics and intermixing between plasma-gas species in laser ablation cerium plasmas, advancing our understanding on optical signatures of nuclear-relevant materials to enable in-field measurement capabilities. [ABSTRACT FROM AUTHOR]

Plutonium research has been stifled by the significant number of administrative controls and safety procedures, space and instrumentation limitations in radiological gloveboxes, and the potential for personnel and equipment contamination. To address the limited number of spectroscopic studies in Pu-bearing compounds in the current scientific literature, this work presents the use of double-walled cells (DWCs) in "clean" buildings/laboratories as an alternative to research in radiological gloveboxes. This study reports the first laser-induced breakdown spectroscopy (LIBS) experiments of a PuO2 pellet contained within a DWC, where the formation of elemental (atomic and ionic) species as well as the evolution from elemental to molecular products (Pu x O y) was measured. Raman spectroscopy was also used to characterize the surface of the ablated pellet and the particulates deposited on the window of the inner cell. The full width half-maximum of the T2g band enabled us to obtain an estimate of the temperature at the pellet surface after the ablation pulse and the particulates based on the crystal lattice disorder. Particulates deposited on the window of the DWC during laser ablation were characterized using scanning electron microscopy, where molten irregular particulates and spheroids were observed. This exciting research conducted in a DWC describes our initial attempts to incorporate LIBS in the arsenal of spectroscopic tools for nuclear forensics applications. [ABSTRACT FROM AUTHOR]

Femtosecond laser ablation of metals generates a strongly ionized plasma plume near the irradiated surface. The resulting plasma shielding effect can reduce subsequent laser energy deposition and lower nanomachining efficiency, especially during multi-pulse irradiation. Understanding the spatiotemporal evolution of the laser-induced plasma and its associated shielding effect is, therefore, crucial. A hybrid two-temperature and direct simulation Monte Carlo (TTM-DSMC) computational model is developed in this study, which synergistically couples the ultrafast laser–metal interaction physics and the plasma collisional transport. The model simulates the plasma properties including electron density, temperature dynamics, reflectivity, and energy attenuation throughout the plume expansion process from femtosecond to nanosecond timescales. A complex "penguin-shaped" plasma plume with internal shockwaves is observed due to the effects of double-pulse irradiation. Significantly enhanced plasma reflectivity and reduced laser energy deposition demonstrate the accumulated shielding effect, which increases with higher plasma density accumulation when the pulse separation is insufficient. Our model provides valuable theoretical guidance for optimizing processing parameters to enhance efficiency and precision in femtosecond laser machining. The integrated TTM-DSMC approach could also facilitate the study of laser-induced plasmas in other contexts like material characterization and nanoparticle synthesis. [ABSTRACT FROM AUTHOR]

This paper deals with double-pulse laser-induced breakdown spectroscopy (LIBS) underwater, which is a promising analytical method for elemental analysis in the deep sea up to a water depth of 6000 m. A double-pulse laser with a wavelength of 1064 nm is used, which provides a pulse energy of up to 266 mJ for each laser pulse (in single pulse mode), a pulse width of 5–7 ns and a pulse delay in the range of 0.5 to 20 µs. In the double-pulse LIBS method, the first laser pulse creates a cavity on the material surface, and then the second laser pulse forms the plasma in this cavity. It is expected that the plasma is affected by the cavity's size and lifetime. For this reason, the influence of focus position, pulse energy and pulse delay on the cavity and plasma formation at shallow water depth has been investigated. [ABSTRACT FROM AUTHOR]

A stand is described that is designed to study the emission properties of laser plasma in the extreme ultraviolet range (EUV) formed on liquid jet targets. To form a jet target, a pulse valve and capillaries of various diameters are used. A Nd:YAG laser is used (with a wavelength of 1064 nm, a pulse duration of 11 ns, a frequency of up to 10 Hz, and a pulse energy of 500 mJ) to excite laser plasma. To investigate the emission spectra, a mirror X-ray spectrometer calibrated in absolute units, an Aurora 4000 visible-range spectrometer, and a microscope operating in the EUV range are used. Photographing of the formed liquid jets is also provided. The design of the stand and its main parameters are presented. The results of the first experiments to study the processes of liquid outflow from various nozzles into vacuum are also presented. [ABSTRACT FROM AUTHOR]

Measurement of the temporal evolution of laser-produced plasma temperature is very important for many of its applications, and several plasma diagnostic tools are routinely used by researchers. However, it is very challenging to measure the properties of the plasma at the early and late times of its evolution using a single diagnostic tool. In this study, we combined emission and laser absorption spectroscopy to compare the excitation temperatures of a laser-produced uranium plasma system. Several U I transitions in the near-infrared spectral range (775–800 nm) were considered, and the Boltzmann plot method was used to measure the excitation temperatures using both emission and absorption spectroscopy. Emission spectroscopy provided early-time temperature measurements of the plasma up to times 2–20 µs, while absorption spectroscopy provided temperature measurements at late times of plasma evolution (for times 5–80 µs). The emission and absorbance of U I transitions were found to follow the Boltzmann distribution, indicating the plasma is likely in the state of local thermodynamic equilibrium even at late times of its lifetime. The emission and absorption-based time-resolved excitation temperatures demonstrated good agreement at earlier times (≤15 µs) in the overlapped temporal region, while a deviation in the measured values was seen at times (≥15 µs), and potential reasons for such a disagreement are discussed. [ABSTRACT FROM AUTHOR]

We demonstrated spectral control of beyond extreme ultraviolet (B-EUV) emission at a central wavelength of 6.76 nm from a gadolinium (Gd) laser-produced plasma. The highest spectral purity (SP) was 5.1% under dual 1-μm laser pulse irradiation. It doubled compared to a value of 2.4% attained under single laser pulse irradiation of solid density Gd because of the reduction in optical depth. The highest maximum SP was higher than that obtained using a mid-infrared laser at 10.6 μm. The SP for the 150-ps main laser was also higher than that for 6-ns main laser irradiation. Our approach can be extended to mid-infrared solid-state laser-produced plasmas (LPPs) using driving laser wavelengths ranging from 2 to 9 μm for efficient B-EUV source development. [ABSTRACT FROM AUTHOR]

Liquid aluminum containing the important alloying element magnesium in varying concentrations was analyzed using in-situ laser-induced breakdown spectroscopy (LIBS). Magnesium emission shows an exponential dependence on melt temperature that correlates well with the expected partial pressure of magnesium above the aluminum melt. Furthermore, comparison with LIBS measurements on corresponding solid samples supports the conclusion that a significant part of Mg emission from liquid metal samples originates from the vapor phase above the metal surface. Simultaneously, curves of growth measured over four orders of magnitude in Mg concentration reveal a level of self-absorption for liquid aluminum samples that is stronger than for solid aluminum samples having a corresponding Mg concentration, and beyond what is expected from conventional plasma models. The implications for measurements of volatile species in liquid metals in general are discussed. Graphical abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

The theory of the terahertz (THz) waves emission from a near-critical plasma slab under the action of the focused p -polarized laser pulse is developed. The spectral, angular and energy characteristics of the THz signal are studied as functions of the focusing degree and the incidence angle of laser radiation, as well as the density and thickness of the plasma slab. It is shown that the extremely strong increase in the energy of the THz signal (up to millijoule level) and conversion rate (up to 10 %) occurs at the almost normal incidence of the ultra-short, tightly focused p -polarized laser pulse on the thin plasma slab with the near-critical density and rare electron collisions. [ABSTRACT FROM AUTHOR]

The formation of laser-induced plasma on a solid target depends strongly on the laser pulse parameters and the ambient conditions. In this work, the characteristics of laser-induced plasma generated in water and in air were investigated with two laser pulse durations of 6 ns and 17 ns. It was shown that the responses of laser-induced breakdown spectroscopy (LIBS) signals on the laser pulse duration in water and in air are different. In water, the 17 ns laser induces a brighter plasma and a stronger LIBS signal, whereas in air, the 6 ns laser is better. Such differences were attributed to the different plasma growth mechanisms in water and in air. The plasma growth in air is driven by strong laser-supported absorption waves, where the 6 ns laser with a higher peak irradiance corresponds to a stronger shock wave and more efficient heating on the plasma. Whereas for plasma growth in water, a great amount of laser energy is consumed in the material phase transitions, and in the mechanical effects of bubble expansion and shock wave propagation. The underwater plasma is far less heated by the laser pulse, and more easily suffers from the multiple breakdowns of water producing multiple shock waves and multi-plasmas. By using a longer laser pulse, which has a lower peak irradiance, the underwater plasma can absorb more laser energy over a longer laser pulse duration, and the multiple breakdown phenomenon can be suppressed. This results in a higher quality of underwater LIBS signals. The present work gives insights into the mechanism of plasma growth in water and in air, and provides suggestions for the choice of laser pulses in the relevant LIBS analyses. [ABSTRACT FROM AUTHOR]

It is indispensable to accurately and sensitively identify and analyze the elemental composition of human blood serum. In the current study, human blood serums were analyzed for elements utilizing orthogonal dual pulse laser-induced breakdown spectroscopy (DP-LIBS) setup in He gas environment. Experimentally, a fundamental pulse Nd:YAG laser (1064 nm, 7 ns) was irradiated just above the material target to induce a luminous gas plasma. A third harmonic pulse Nd:YAG laser (355 nm, 7 ns) was subsequently focused on the material surface to initiate a target plasma to ablate the atoms from the blood serum film to be sent to the gas plasma region. Double pulse LIBS technique has been successfully applied to increase the LIBS signal intensity up to 8 folds of major, minor, and trace components in human blood serum. Furthermore, a number of emission lines that were indistinctly detected by single pulse LIBS were accurately identified with the use of the DP-LIBS. A variety of components from the human blood serum have been analyzed both qualitatively and quantitatively. Element concentrations measured in human blood are to be 8360 ppm, 219 ppm, 581 ppm, 785 ppm, 343 ppm, 293 ppm, and 12 ppm for C, Ca, K, Mg, P, Na, and Fe, respectively. The LIBS outcome results are in excellent agreement with the results acquired by applying the standard XRF technique. [ABSTRACT FROM AUTHOR]

In this review, we attempt to provide a brief account of laser-induced breakdown spectroscopy (LIBS) methodology and technological developments. We also summarize various methods adopted for exploiting LIBS. Besides, a brief overview of combination of LIBS in conjunction with other methods is also given. [ABSTRACT FROM AUTHOR]

In this work, we investigate the properties of the plasma induced by focusing a high-power laser beam on an aluminum target that was cooled by a helium refrigerator from room temperature down to 20 K. Fast, streak photographs of the plasma were taken at different temperatures and laser energies. From the images obtained, position-vs-time plots were made for each experiment, and from them, the speed was calculated. Additionally, narrowband interference filters were employed to image the dynamics of ions and neutrals separately. It was found that the plasma plume has two distinct speeds: that of its center and that of the outer edge. For unfiltered images, the former has values within the interval 6.2 to 9.1 km/s, while the latter can reach speeds of the order of hundreds of km/s. It was found that the plume of a target cooled to 20 K has a length that is 8%–12% less than the corresponding size at room temperature. Chilling the target did not seem to affect significantly either the plume's speed of expansion or the size of the crater produced. Lower bounds were estimated for the momentum imparted to the ejecta and the specific impulse. The latter can reach a 920-s level, nearly twice as much the amount obtained with chemical rocket fuel. [ABSTRACT FROM AUTHOR]

The mechanism of double-pulse laser irradiation under spatial confinement remains unclear due to complex plasma plume dynamics and multiple shock wave interactions. In this study, coupling of spatial confinement and double-pulse irradiation was investigated using fast photography, laser shadowgraphy, and spectroscopy. The experimental results demonstrated unique dynamic processes of plasma plume and shock waves, confirming that the plasma plume was eventually reshaped into a jet-like structure, and the combined enhancement effect can be regulated through different parameters, including inter-pulse delay and plate spacing. The inter-pulse delay dictates the primary mechanism of the secondary pulse's interaction with the initial plasma and the target surface; as it increases, plasma front absorption decreases while target surface ablation intensifies. Plate spacing determines the delay from laser incidence to plasma plume compression; along with the inter-pulse delay, it influences whether the secondary pulse generates a second-generation shock wave that merges with the initial shock wave for compression or performs a secondary compression after the first. Compared to double-pulse irradiation alone, combined enhancement increased emission intensity of Fe, Ni, and C spectra by up to 4.1 times accompanied by the increase in plasma temperature. The R2 of calibration curves was increased, and the sensitivity for trace components Cr and C was improved with limits of detection reaching 255 and 659 ppm. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is a promising technique to monitor carbon emissions in post-combustion flue gas. However, its measurement accuracy is susceptible to variations in gas temperature. In this work, a mid-level data fusion method integrating spectral and acoustic signals generated by laser-induced plasmas (LIPs) was proposed to improve the measurement accuracy. This method utilizes the high sensitivity of acoustic signals to variations in gas temperature, enabling a correction of temperature effects. The acoustic features were extracted from both the time-domain waveforms and frequency spectra, while the spectral features were selected using a SelectKBest method. These features were fused into a new array, on whose basis multivariate regression models including Partial Least Squares (PLS), Support Vector Machines (SVM), and Random Forest (RF) were trained. Data fusion significantly improved the predictive precision and trueness of SVM and RF models, with the RF model achieving the best performance: a coefficient of determination (R2) of 0.9941, a root-mean-square error (RMSE) of 0.4864, a mean absolute error (MAE) of 0.2587, and a mean absolute deviation (MAD) of 0.0980. Shapley additive explanation (SHAP) analysis revealed that in the RF model, the acoustic features that exhibited higher temperature sensitivity could be more frequently selected in the training process and thus had greater impacts on model outputs, which can better correct for the gas temperature effect. Furthermore, the potential of this method in industrial applications was demonstrated in an unsteady flow. [ABSTRACT FROM AUTHOR]

The storage and management of nuclear waste materials require the detection of uranium, but traditional analytical methods are unsuitable for radioactive environments. The enhancement methods of uranium in glass matrices using fiber-optic laser-induced breakdown spectroscopy are still underdeveloped. Using an optical diagnostic system coupled with fast photography, shadowgraphy, and optical emission spectroscopy, the evolution of laser-induced plasma generated from a glass matrix under spatial confinement is studied. The plasma evolution image illustrates the temporal consistency between the compression of plasma width and the enhancement of luminescence intensity. Two enhancements were observed when the plate spacing was smaller than the plasma, which might be due to the high density of the core plasma or a synergistic effect of plasma expansion and shockwave confinement. Under spatial confinement, there is a 3–4-times enhancement in the intensity of uranium spectral lines and a 2–4 times enhancement in the signal-to-noise ratio. Several calibration curves are established under spatial confinement based on U II 409.01 nm, U II 367.01 nm and U I 358.48 nm. The lowest limit of detection (LOD) of uranium reaches 95 ppm, which supports the application of FO-LIBS in the detection of uranium-containing nuclear waste materials. [ABSTRACT FROM AUTHOR]

In this investigation, a spectroscopic optical emission test was used to investigate the characteristics of gold plasmas that were produced in the surrounding environment using an Nd: YAG system at a wavelength of 1064 nm and had an energy output that varied from 400 to 600 mJ. The emission spectrum profiles of (Au) were analyzed and recorded using a spectrometer to aid in the extraction of vital plasma features (i.e., T e and n e ). Plasma temperature was determined using the Boltzmann plot method, and electron density was determined using the Stark broadening method. The temperature was between (0.91 and 0.94) eV, while the electron density ranged between (4.79 and 5.26) × 1 0 1 7 cm − 3 . The rest of the plasma parameters were calculated by the mathematical equations of the method used (Boltzmann Plott). [ABSTRACT FROM AUTHOR]

In this study, we have investigated the relationship between the plasma temperature in remote laser-induced breakdown spectroscopy (LIBS) experiments and the hydrophobic properties of silicone rubber insulators (SIRs). Contact angle and LIBS measurements were conducted on both artificially-aged (accelerated aging) and field-aged SIRs. This study reveals a clear connection between plasma temperature and the properties of aged SIRs on artificially-aged SIR specimens. Specifically, the plasma temperature exhibits a consistent increase with the duration of the accelerated aging test. The hydrophobicity of the artificially-aged SIRs was assessed by performing contact angle measurements, revealing a decrease in the hydrophobicity with increased aging test duration. Furthermore, we extended our investigation to the study of nine field-aged SIRs that had been in use on 150 kV overhead transmission lines for 0 to 21 years. We find that the laser absorption and hardness of the material do not relate to the plasma temperature. In summary, we observe a direct connection of plasma temperature to both contact-angle measurements and operation time of the in-service insulators. These results strongly suggest the potential use of LIBS for remotely evaluating the hydrophobicity and aging degree of silicone rubber insulators, thus assessing their real-time on-site operational quality. [ABSTRACT FROM AUTHOR]

The ignition and flame propagation in an axisymmetric supersonic combustor were investigated. The laser-induced plasma was employed to ignite the supersonic inflow with a speed of Mach 2.5 and a total temperature of 1486 K. A direct-connect axisymmetric model scramjet with a fully transparent glass combustor was built, which enabled the circumferential and axial flame propagation in the cavity-based axisymmetric supersonic combustor to be visualized by the high-speed photography from the endoscopic and external views, respectively. An initial flame kernel is produced by the laser-induced plasma and propagates to the cavity leading edge along the axial direction. The establishment of the cavity shear-layer flame facilitates circumferential flame propagation. The circumferential flame propagation is coupled with the axial propagation, eventually generating a loop-shaped flame with a central-hole. Acceleration of the flame propagation can be observed, especially when the global equivalence ratio is increased. A plausible explanation for the flame propagation in the axisymmetric supersonic combustor was found using URANS numerical simulation. The axisymmetric cavity generates a low-speed loop-shaped recirculation region and thickened cavity shear-layer with an appropriate local equivalence ratio, resulting in the simultaneous axial and circumferential flame propagation. The increased temperature in the cavity and the thickened cavity shear-layer during the flame propagation produce a more intense heat release and mass transfer, leading to faster flame propagation. [ABSTRACT FROM AUTHOR]

This study explores the potential of utilizing microwaves to sustain the expansion of transient laser ablation plasma of Zr target. By application of microwaves on the plasma, we observe a significant enhancement with a two to three order of magnitude increase in the plasma emission intensity, and 18 times increase in the plasma's spatial volume. We investigate the temperature change of the plasma and observe that it decreases from 10,000 K to approximately 3000 K. Electron temperature decreased with volume expansion owing to increased surrounding air interaction, while the plasma can be sustained in air using microwaves. The increase in electron temperature during temperature drop is indicative of non-equilibrium plasma. Our results emphasize the contribution of microwaves in promoting enhanced emission and plasma formation at controlled, low temperature, thereby demonstrating the potential of microwaves to enhance the accuracy and performance of laser-induced breakdown spectroscopy. Importantly, our study suggests that microwaves could also mitigate the generation of toxic fumes and dust during ablation, a critical benefit when handling hazardous materials. The system we've developed is highly valuable for a range of applications, notably including the potential to reduce the possible emergence of toxic fumes during the decommissioning of nuclear debris. [ABSTRACT FROM AUTHOR]

We present the results of joint measurements of electron density ( n e ), temperature ( T e ), and emission spectra of an Nd:YAG-driven tin plasma. Collective Thomson scattering provides space- and time-resolved n e and T e data during drive laser irradiation, and extreme ultraviolet (EUV) emission spectra, which is space-resolved in the target normal, are measured using a flat-field grazing incidence spectrometer (GIS). As the distance from the target increased, the emission intensity quickly decreases, and the peaks of the spectra gradually shift to longer wavelengths. This can be explained by the rapid decrease in n e , and thus, self-absorption, with an increase in distance. We obtain the EUV spectra by calculating the transfer of photons along the line-of-sight of the GIS, using theoretical emissivity and opacity, and applying the measured spatial distribution of n e and T e . The results quantitatively demonstrate that the self-absorption effect is significant; the emission from the core regions is mostly reabsorbed by the surrounding plasma. The calculated spectra are compared with the measured spectra. While good agreement is achieved in the spectral region of 13.3 and 15.3 nm, considerable differences are found in the 12.5–13 and 15.5–17.5 nm region. The results demonstrate the significance of this joint measurement for further validation of the atomic process model considering self-absorption effect, which is critical for the future high-density, solid laser-driven EUV source. [ABSTRACT FROM AUTHOR]

Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) is an optical emission technique based on the laser-induced plasma (LIP) on a sample after the deposition of plasmonic nanoparticles (NPs) on its surface. The employment of the NPs allows an enhancement of the signal with respect to the one obtained with the conventional laser-induced breakdown spectroscopy (LIBS) enabling an extremely high sensitivity and very low limits of detection compared with the LIBS performance. Recently, NELIBS was used for monitoring the NP protein corona formation. As a matter of fact, the NPs in the presence of proteins adsorbed on the surface change their surface properties, therefore the sensing of protein corona formation was possible because of the strong dependence of NELIBS effects on the NP organization on the substrate, which in turn is deeply affected by the surface properties of the NPs. A correlation was found between NELIBS enhancement and the structure of the NP–protein conjugate in terms of protein content absorbed on the NP surface. An interesting question that was not yet exploited regards the role of LIP during the NELIBS when the NPs are covered with proteins. Since the presence of organic matter can strongly quench the LIP emission, the study of the LIP properties during protein corona sensing by NELIBS is of interest for two main reasons: (i) to understand whether the plasma parameters can vary in the presence of proteins adsorbed on the NP surface and (ii) to investigate how and if the plasma parameters themselves can influence the NELIBS processes. With this aim, the study of plasma parameters, i.e., electron densities and temperatures, during the sensing of NP protein corona by NELIBS is presented and discussed. The NPs used during these experiments were ultrapure gold NPs (AuNPs) produced by pulsed laser ablation in liquid, which are stable without any stabilizer. The human serum albumin protein is used to form AuNP–protein conjugates further deposited on a titanium target in NELIBS measurements. Dynamic light scattering, surface plasmon resonance spectroscopy, and laser Doppler electrophoresis for ζ-potential determination were employed to monitor the protein coverage of NP surface in the conjugate solutions before the NELIBS measurements. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

Polarized emission carries captivating information and can help in understanding various elementary processes involving collisions within the plasma as well as in radiative transitions. In this work, we investigate the spatio-temporal dependence of the emission anisotropy of a nanosecond laser produced aluminium plasma at 100 mbar background pressure. We observe that the anisotropy of the emission spectra exhibits interesting spatio-temporal characteristics, which in turn depends on the charge state of the emitting species. The degree of polarization (DOP) is found to reverse its sign along the plume propagation direction. The observed behaviour in the DOP appears to be due to the contribution from various atomic processes involved. Closer to the sample the contribution from the self-generated magnetic field predominantly affects the polarization. On the other hand, the effect of the self-generated magnetic field on the observed polarized emission is insignificant as the plume propagates away from the sample. This is of particular interest in polarization resolved laser induced breakdown spectroscopy (PRLIBS) as the spatio-temporal profile of the degree of polarization has to be properly taken into account prior to the spectral analysis. [ABSTRACT FROM AUTHOR]

Air pressure is one of the key factors affecting laser-induced breakdown spectroscopy (LIBS), and the mechanism of its influence on the spatial–temporal evolution of laser-induced plasma (LIP) is still not fully understood due to complex physical processes. In this study, the spatially and temporally resolved LIP's spectra at different pressures were collected from the direction of laser incidence, and the radial distribution characteristics of LIP along the target surface under the influence of air pressure were studied. Furthermore, the spatial–temporal evolution of the radial distribution of the electron density n e and electron temperature T e was studied using Stark broadening and a Boltzmann plot. Finally, the radial distribution of LIP satisfying the McWhirter criterion and the influence of air pressure on its spatial–temporal evolution were studied. It was found that air pressure has a significant effect on the radial distribution of LIP. The spectral intensity, electron density n e, and the electron temperature T e of the LIP decrease faster against distance r from the LIP core and slower with the delay time T d in a higher air-pressure environment. Furthermore, the LIP will gradually fail to satisfy the McWhirter criterion with the increase in the radius r and delay time T d; in addition, the lifetime of LIP, which satisfies the McWhirter criterion, is longer at higher pressure. This study is helpful in clarifying the influence of air pressure on the spatial–temporal evolution of LIP, optimizing the experimental parameters of LIBS, and providing a reference for application of LIBS. [ABSTRACT FROM AUTHOR]

The paper discusses the results of studying the emission spectra and absolute radiation intensities of laser plasma generated by laser pulse on a xenon gas-jet target. A Nd:YAG laser, λ = 1064 nm, τ = 5.2 ns, Epulse = 0.8 J was used. The spectral range 3–20 nm was studied. Gas-jet targets were formed by a supersonic conical nozzle. Emission spectra of laser plasma were obtained and interpreted. Absolute radiation intensities were determined in a number of spectral bands under various conditions of gas-jet target excitation. [ABSTRACT FROM AUTHOR]

Laser-induced plasma from an aluminum nitride (AlN) target into a vacuum and nitrogen ambience has been investigated by means of time-integrated and time-resolved optical emission spectroscopy (OES), to understand the physicochemical process during plasma expansion. A Q-switched Nd-YAG laser was used to create AlN plasma at different laser fluences (7–31 J cm−2). The emission spectra recorded in a vacuum are dominated by neutral and ionized aluminum emission lines from Al, Al+ and Al2+ species, while the emissions from atomic nitrogen species were weakly observed. The time of flight of Al+ in a vacuum shows evolution from a single component to double components and back to a single component with increasing laser fluence. A plateau was observed for the expansion velocities of Al2+ at higher fluences. To jointly study the effect of nitrogen gas pressure (0.5–4 mbar) and laser fluence on the evolution of plasma composition, space-and-time-resolved emission of AlN plasma species was employed. At 1.5 mbar N2 pressure, the time of flight of species showed evolution of triple components for Al and Al+ and double components for Al2+ and N, N+ and N2+ species. The kinetics of the latter were followed. [ABSTRACT FROM AUTHOR]

In this study, the effect of environment gas and working pressure of laser-induced breakdown spectroscopy from ZnO: Al composite target (AZO) enhanced by an external magnetic field on the magnetized characteristics and emission spectra of plasma were investigated. The plasma was induced by a Q-switched nanosecond Nd: YAG laser at a constant pulse laser energy of 300 mJ at different pressures of 0.08, 0.2, 0.4, and 760 Torr in air and argon gas. The atomic and ionic emission lines increased in intensity directly with the working pressure. The plasma temperature (Te) and electron number density (ne) were determined at the different environmental conditions according to the intensity-ration method, and Stark broadening effect, respectively. Both ne and Te increased with increasing pressure and with the presence of magnetic field as a result of confining effect. The line profile appeared with high broadening at atmospheric pressure compared with vacuumed plasma. The Larmur radius and confinement factor β increased with working pressure. From another hand, using Ar instead of air caused slightly reduced ne at low pressure, while Te has the opposite behavior. [ABSTRACT FROM AUTHOR]

In this work, the main peculiarities of Laser Induced Plasma (LIP) in liquid have been investigated by comparing the evolution of the LIP in water and in air. To this end, fast shadowgraphy and temporally resolved emission spectroscopy were used. The experimental results reveal a scenario where plasma under water remains in a high-density state, characterized by the condensation of electronic levels as a consequence of the confinement effect of the surrounding water. In this case, the plasma emission spectrum consists of continuum radiation. In contrast, LIP in air expands, reaching an ideal plasma state in a few hundred nanoseconds. In this condition, excited electronic levels are enabled and the spectrum is characterized by discrete emission lines, according to the Boltzmann statistics. These differences allow LIP in liquid and gas to be used in a wide variety of applications, ranging from analytical chemistry to nanomaterial production. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown and subsequent plasma are produced in ambient air in the proximity of an aqueous surface using a Nd:YAG Q-switched laser at 1064 nm with a pulse width of 9 ns and a delivered focused input energy of 170 mJ. The distance between the focal point of a 10 cm convex lens and the aqueous surface is 4 mm with laser propagation perpendicular to the surface. Using an intensified CCD camera attached to a 1-m spectrometer, spatial and wavelength-resolved plasma emission data are obtained for delay times after breakdown ranging from 50 ns to 10 μs with a gate window typically 5 ns. Plasma electron density is determined by applying Lorentzian fitting and FWHM extraction to three Stark-broadened spectral lines: N II 3P-3Do multiplet (593.85 nm), Hα (656.27 nm), and the Na D doublet (589.00 and 589.59 nm). One-dimensional spatially resolved measurements of the total emission intensity and electron density are obtained by binning the camera image along the laser axis in intervals of 250 μm and are reported as a function of time from 50 ns to 10 μs. Two plasmas are ignited from a single laser pulse; one from laser breakdown at the water surface and the other a few nanoseconds later from laser-induced air breakdown at the focal point of 4 mm above the water surface. Comparisons between the evolution of the air plasma near and far from the water surface are presented along with data for the water surface plasma itself. [ABSTRACT FROM AUTHOR]

A series of experiments are conducted for the study of time-dependent variations of major emission from the metastable excited He generated in various experimental conditions. Different Nd:YAG laser pulse widths and pulse energies, as well as purity of the He gas, are employed for studying quenching effects including the use of a Cu target in an experimental condition for spectrochemical analysis. It is found that in all cases investigated, the metastable excited He atom (He*) associated with the triplet He I 587.5 nm emission line has the unquestionable dominance over another triplet emission line of He I 388.8 nm and the singlet He I 667.8 nm emission. Further analysis of the present data combined with the results of previous studies suggested that the energy transfer between He atoms via the Penning-like collision-induced energy transfer process has so far remained less than appropriately addressed. It is strongly argued and demonstrated in this work that this underlying physical process is likely the moving force leading to the repeated He ionizations responsible for the self-propelled multiple amplification of the triplet He I 587.5 nm emission intensity particularly at the early stage of the shock wave formation. This study has convincingly demonstrated that the Penning-like collision-induced energy transfer process can also effectively take place between He* and the ablated atoms, implying its usefulness for spectrochemical laser-induced plasma spectroscopy analysis. [ABSTRACT FROM AUTHOR]

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Aiming to tackle the problems of low classification accuracy, difficult data processing, long analysis time, and the influence of subjective consciousness of traditional Baijiu (Chinese liquor), this paper reports a method based on the combination of laser-induced breakdown spectroscopy with high-frequency ultrasonic atomization system (AS-LIBS) and optimized grid search cross validation (Opt-GSCV) for high-precision and rapid classification of Baijiu of different dimensions. Multi-dimensional high-precision classification of 23 Baijiu samples with different series, degrees, and production dates from Shanxi Xinghuacun Fen Wine Factory Co., Ltd was performed. By studying the growth and evolution mechanism of plasma generated by laser excitation, a new method of Baijiu spectral signal acquisition was realized by combining LIBS with Baijiu detection. Aiming at addressing the shortcomings of high breakdown thresholds and poor signal stability due to the direct breakdown of Baijiu with high ethanol content, a high-frequency atomization system based on ultrasonic technology is proposed to realize the efficient extraction of Baijiu plasma spectral signals. With regard to the selection of the number of nodes, weights and thresholds of the implicit layer of the back-propagation (BP) network, an optimization model based on the combination of the particle swarm optimization (PSO) algorithm combined with the genetic algorithm (GA) is proposed to realize the construction of the BP optimal network architecture. By constructing a secondary optimization seeking network model based on OptGSCV, the technical problem of mismatch between optimal parameter selection and optimal network construction is solved, and a new network integrating an intelligent qualitative analysis algorithm and a traditional classification algorithm is realized. The experimental results show that the proposed OptGSCV quadratic optimization network combined with the AS-LIBS multidimensional Baijiu high-precision classification model not only introduces an innovative and high-efficiency detection method for the Baijiu industry, but also provides important technical support and new ideas for the key areas of food safety production and Baijiu quality control. [ABSTRACT FROM AUTHOR]

Terahertz radiation from two-color femtosecond laser-induced gas filament is investigated in a wide range of the ambient gas pressure from 0 to 606 kPa (i.e., 0–6 atm). We observed that the output energy of terahertz radiation first increased quickly to the strongest strength at the optimal pressure around 25 kPa then decreased gradually with increase of the gas pressure. We found a linear dependence of the time delay of the terahertz signals on increasing gas pressure under a wide range of gas pressure and nearly unchangeable plasma density profile of the filament in the high pressure range from ~ 50 kPa to 606 kPa if keeping the same pump laser energy. Our numerical simulation results reproducing the experimental dependence of decreasing terahertz strength on the increasing gas pressure in this high pressure range indicate that this dependence could be attributed mainly to the decreasing coupling of the two-color laser pulses in the plasma filament due to different changes of their propagating velocities in the ambient gas with increasing pressure. Our results would be helpful for understanding deeply the mechanism of terahertz radiation and remind a possible strategy for improvement of terahertz output under higher gas pressures and pumped by more laser energies. [ABSTRACT FROM AUTHOR]

This work explores the enhanced spectroscopic characterizations of the soil plasma through the magnetic field-assisted laser-induced breakdown spectroscopy (LIBS) technique and its dependence upon laser fluence. The laser-induced soil plasma has been produced by the employment of Nd:YAG laser (1064 nm) on the surface of the pelletized river soil samples in the absence and presence of a magnetic field of 0.66 T at different laser fluences (30–61 J/cm2). Various elements particularly trace elements (arsenic, chromium, manganese, barium, titanium, cobalt, and strontium) were detected in the soil samples, where an enhancement factor of up to 6 times is achieved with the application of a magnetic field to LIBS. The plasma parameters like electron temperature (Te) and electron number density (ne) show an increasing trend with the laser fluence and then decline slightly after 51 J/cm2 laser fluence but with higher values of these parameters under the magnetic field. The better spectroscopic results are attributed to the magnetic confinement of the plasma, confirmed by the plasma parameter βt < 1. In addition, the threshold laser fluences have been estimated for the soil sample as ~ 6 J/cm2 and ~ 11 J/cm2 with and without magnetic field, respectively. The variation in Inverse Bremsstrahlung co-efficient and plasma frequency as a function of laser fluence is also reported. Improved spectroscopic results of magnetic field-assisted LIBS demonstrate it as a promising tool for the detection of multi-elements particularly trace elements in river soil samples. [ABSTRACT FROM AUTHOR]

Two-color laser field-induced plasma filaments are efficient broadband terahertz (THz) sources with intense THz waves emitted mainly in the forward direction, and they have been investigated intensively. However, investigations on the backward emission from such THz sources are rather rare. In this paper, we theoretically and experimentally investigate the backward THz wave radiation from a two-color laser field-induced plasma filament. In theory, a linear dipole array model predicts that the proportion of the backward emitted THz wave decreases with the length of the plasma filament. In our experiment, we obtain the typical waveform and spectrum of the backward THz radiation from a plasma with a length of about 5 mm. The dependence of the peak THz electric field on the pump laser pulse energy indicates that the THz generation processes of the forward and backward THz waves are essentially the same. As the laser pulse energy changes, there is a peak timing shift in the THz waveform, implying a plasma position change caused by the nonlinear-focusing effect. Our demonstration may find applications in THz imaging and remote sensing. This work also contributes to a better understanding of the THz emission process from two-color laser-induced plasma filaments. [ABSTRACT FROM AUTHOR]

In the work that is being presented here, the effect of sample thickness and laser irradiance on the reduction of the signal-to-background ratio SBG and the plasma parameters, specifically electron temperature and electron density, is being investigated using back-reflection-enhanced laser-induced breakdown spectroscopy (BRELIBS). Copper and silver discs that had been highly polished were attached to the back surface of the glass target, and the Nd-YAG laser beam that was focused on the front surface of the target was tuned to its fundamental wavelength. The thicknesses of the transparent glass samples that were analysed were 1 mm, 3 mm, and 6 mm. One is able to achieve a range of different laser irradiance levels by adjusting the working distance that exists between the target sample and the focusing lens. The end result of this is that the signal-to-background ratio in the BRELIBS spectra of thicker glass samples is significantly lower as compared to the ratio in the spectra of thinner glass samples. In addition, a significant influence of modifying the laser irradiance (by increasing the working distance on the SBG ratio) is seen at various glass thicknesses for both BRELIBS and LIBS, with BRELIBS having a better SBG. Nevertheless, the laser-induced plasma parameter known as the electron temperature has not been significantly impacted by the decrease in the glass thickness. [ABSTRACT FROM AUTHOR]

Single-shot ultrafast multi-frame imaging technology plays a crucial role in the observation of laser-induced plasma. However, there are many challenges in the application of laser processing, such as technology fusion and imaging stability. To provide a stable and reliable observation method, we propose an ultrafast single-shot multi-frame imaging technology based on wavelength polarization multiplexing. Through the frequency doubling and birefringence effects of the BBO and the quartz crystal, the 800 nm femtosecond laser pulse was frequency doubled to 400 nm, and a sequence of probe sub-pulses with dual-wavelength and different polarization was generated. The coaxial propagation and framing imaging of multi-frequency pulses provided stable imaging quality and clarity, as well as high temporal/spatial resolution (200 fs and 228 lp/mm). In the experiments involving femtosecond laser-induced plasma propagation, the probe sub-pulses measured their time intervals by capturing the same results. Specifically, the measured time intervals were 200 fs between the same color pulses and 1 ps between the adjacent different. Finally, based on the obtained system time resolution, we observed and revealed the evolution mechanism of femtosecond laser-induced air plasma filaments, the multifilament propagation of femtosecond laser in fused silica, and the influence mechanism of air ionization on laser-induced shock waves. [ABSTRACT FROM AUTHOR]

Fast ionization wave (FIW), a postbreakdown phenomenon of laser-induced plasma, is observed for a laser intensity of 1011–1013 W/m2 using the CO2 laser pulse in the atmospheric pressure condition. FIW is distinguishable as "overdriven detonation" according to Raizer's Chapmann-Jouguet detonation theory because FIW is known as the type of laser-absorption wave that has a higher propagation velocity than the laser-supported detonation wave (LSDW). Some reports have described the expansion of FIW using a solid-state laser. Nevertheless, the threshold phenomena between FIW and LSDW are not fundamentally understood. This study used the high-speed visualization and optical emission spectroscopy to investigate the transition of the laser-absorption wave in argon gaseous form. To elucidate the physics of the transition threshold, a 5 J CO2 pulse laser, an Echelle spectrometer, and an intensified CCD camera are used for the quantitative investigation of the plasma temperature and density. Results demonstrate that the FIW front had an electron temperature of 0.7 eV and an electron number density of 2.5 × 1023 m−3. At the FIW–LSDW transition, the electron temperature increased by 1 eV, and the density decreased by 2.2 × 1023 m−3. Besides, the transition threshold and the existence of local-thermodynamic equilibrium were evaluated based on the electron temperature, and the density was obtained from the spectroscopic experiments. [ABSTRACT FROM AUTHOR]

Increasing extreme ultraviolet (EUV) photon power in laser-produced plasma (LPP) sources is critically important for efficient future nanolithography devices. Enhancing the lifetime of the optical collector system in these devices is another important challenge for reliable and economically feasible devices. In this work, various mechanisms affecting ion acceleration in LPP were investigated to predict the maximum ion energies and flux arriving at the collecting mirror surfaces. Plasma evolution produced by an Nd:YAG laser from Sn targets was studied in detail to predict the dynamics of EUV producing ions and their contribution to the EUV power. The multiphysics fully 3D integrated HEIGHTS computer package was used in this analysis. HEIGHTS simulations of detail plasma evolution and ion kinetic energies were compared with various worldwide experimental data. Excellent agreement was shown regarding the range of ion kinetic energies and their angular distribution as well as recombination processes and their effect on the temporal output of EUV photons. Spatial and charge distributions were predicted for EUV producing ions and ionic debris. The analysis showed that mainly two Sn ions, i.e., Sn XII and Sn XIII, determine the EUV source intensity and spatial location. It was also shown that reducing the laser spot size and increasing the pulse duration allow a significant reduction in ion kinetic energies that is important for a longer lifetime of the optical collection system. [ABSTRACT FROM AUTHOR]

We present measurements from laser-produced plasmas generated using cryogenic Xe targets and quantify the emission characteristics in the soft x-ray region (1 to 6 nm). The system is based on a LN2-cooled rotating drum, which allows for a high repetition rate, and Nd:YAG laser systems with energies up to 325 mJ on-target with pulse lengths of 130 ps, 600 ps, or 6.5 ns. High resolution spectra are measured using a grazing incidence spectrometer, and we present the first quantitative conversion efficiency (CE) measurements for Xe in this range. Data show CE values up to ∼1% at 6 nm and ∼0.08% at 1.5 nm (for 2% bandwidth and 2π solid angle), and there are lower limits on the required laser intensities and energies on target to achieve these efficiencies. In addition, the emission spot size is directly measured at 2 nm (620 eV) using a point-projection slit imaging method, with optimized emission spot sizes of ∼20 μm. [ABSTRACT FROM AUTHOR]

The branching ratio method is usually used to evaluate the optical thinness conditions in laser-generated plasmas, which are important for the application of analytical methods such calibration free laser induced breakdown spectroscopy (CF-LIBS). In this communication, we warn on the possibility that in some circumstances, the branching-ratio method might give results close to the one characterizing optically thin plasma conditions, even in the presence of a substantial self-absorption for the transitions considered. Graphical Abstract [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM) is a highly endothermic process, with its development hindered by the harsh thermocatalytic conditions required. We propose an innovative DRM approach utilizing a 16 W pulsed laser in combination with a cost-effective Mo2C catalyst, enabling DRM under milder conditions. The pulsed laser serves a dual function by inducing localized high temperatures and generating *CH plasma on the Mo2C surface. This activates CH4 and CO2, significantly accelerating the DRM reaction. Notably, the laser directly generates *CH plasma from CH4 through thermionic emission and cascade ionization, bypassing the traditional step-by-step dehydrogenation process and eliminating the rate-limiting step of methane cracking. This method maintains a carbon-oxygen balanced environment, thus preventing the deactivation of the Mo2C catalyst due to CO2 oxidation. The laser-catalytic DRM achieves high yields of H2 (14300.8 mmol h−1 g−1) and CO (14949.9 mmol h−1 g−1) with satisfactory energy efficiency (0.98 mmol kJ−1), providing a promising alternative for high-energy-consuming catalytic systems. Dry reforming of methane (DRM) is a highly endothermic process, often limited by the severe thermocatalytic conditions it demands. Here the authors introduce a novel DRM method that employs a 16 W pulsed laser along with a cost-effective Mo2C catalyst, allowing DRM to proceed under milder conditions. [ABSTRACT FROM AUTHOR]

Sheet Molding Compound (SMC) materials are extensively utilized as high-voltage insulation materials in electrical equipment. SMC materials are prone to aging after long-term operation. Conducting non-destructive testing to assess their electrical and physicochemical properties is crucial for the safe operation of electrical equipment. This study identifies the optimal equipment parameters for testing SMC materials using Laser-Induced Breakdown Spectroscopy (LIBS) technology through experimental investigation and also explores the ablation characteristics of SMC under various laser parameters. The results indicate a significant positive correlation between the ablation depth and laser pulse number, while there is no correlation with single laser pulse energy. However, the ablation area demonstrates a strong positive correlation with both single laser pulse energy and laser pulse number. Additionally, LIBS spectral analysis provides elemental results comparable to Energy Dispersive Spectroscopy (EDS), facilitating the examination of variations in Na, Ti, Fe, Mg, Ca, and C elemental contents with depth. Moreover, an enhanced iterative Boltzmann plot method is suggested for calculating the plasma temperature using 21 Fe I spectral lines and the electron density using the Fe II 422.608 nm line. The variations of these plasma parameters with laser pulse number are documented, and the results show consistent trends, confirming that the laser-induced SMC plasma adheres to local thermodynamic equilibrium. [ABSTRACT FROM AUTHOR]