Laser-induced Breakdown Spectroscopy Approach Research Articles

High repetition-rate laser-induced breakdown spectroscopy combined with two-dimensional correlation method for analysis of sea-salt aerosols

Laser-induced breakdown spectroscopy (LIBS) offers a tantalizing glimpse into real-time, on-the-spot aerosol analysis. Yet, the reliance on traditional lasers, with their limitations in energy and frequency, hampers optimal sample handling, dissociation, and excitation. To address those challenges, we propose a novel tactic: utilize a high repetition-rate (rep.-rate) laser with low pulse energy in combination with the two-dimensional correlation (2D-corr.) technique for sea-salt aerosols analyses. By examining the emission patterns from both the laser pulse train and individual pulses, we recognize distinctive analyte-specific rep.-rate responses, which allowed spectral reconstruction of analytes, avoiding background interferences. This discovery enabled the rep.-rate modulation for a 2D-corr. spectroscopy workflow. Consequently, we successfully differentiated between particle-related and air-species-related spectral components, obviating expensive spectrometers or intensified image detectors. For instance, the Na I at 589 nm stemming from aerosols exhibited an entirely different correlation contribution compared to O I at 777 nm, resulting in reconstructed clean aerosol-spectra without spectral peaks originated from air species. This 2D-corr. aerosol LIBS approach shows promising analytical potential streamlining aerosol particle analysis.

Enlarged Plasma Ablations In Microwave-Enhanced Laser-Induced Breakdown Spectroscopy With Coaxial Multifiber Arrays

This study comprises a comprehensive investigation of the enhancement of laser-induced breakdown spectroscopy (LIBS) using multifiber array configurations and microwave (MW) enhancement. We demonstrated a significant increase in both the emission intensity and Signal-to-Noise Ratio (SNR) through the integration of a six-multifiber setup, resulting in a six-fold increase in broadband emissions. The introduction of MW further augmented this enhancement, exhibiting a two to three orders of magnitude increase in emissions. Remarkably, the combined approach of multifiber LIBS and MW enhancement resulted in a dramatic 2000-time improvement in emission signals. Concurrently, the SNR was enhanced by two to three orders of magnitude. These advancements have opened new avenues for expanding the limits of detection in analytical applications, which is the focus of our ongoing investigation. Our findings have significant implications for various industries including environmental monitoring, materials science, and biomedical research.

Ex-situ quantification of impurity deposition depth on HL-2A divertor graphite tile by laser-induced breakdown spectroscopy

During tokamak discharges, the Plasma Wall Interaction (PWI) would lead to impurity deposition and fuel retention on the surface of the Plasma Facing Materials (PFMs). Laser-induced breakdown spectroscopy (LIBS) has emerged as a promising technique to facilitate in-situ, real-time, online characterization of the impurity deposition and fuel retention on the wall of tokamaks for PWI studies. The purpose of this investigation is to quantify the impurity deposition layer on the graphite tile removed from the dome region of the HL-2A tokamak lower divertor by using the ex-situ LIBS approach. The investigations indicate that the primarily deposited impurity elements are Fe, Cr, Ni, Mn, Ca, Al, Cu, Si, C, which may originate from the stainless steel first wall, divertor, limiter or the siliconized wall conditioning due to the PWI process in HL-2A tokamak. This has been further supported by observing a significantly positive correlation between the Cr, Ni, Mn, Al and Fe elements by spectral cumulative intensity linear regression analysis. The 3D morphology of the laser-ablated craters is reconstructed using a confocal microscope, revealing the laser ablation rates for the deposition layer and the substrate graphite tile to be 348 nm/pulse and 220 nm/pulse, respectively, under the laser fluence of 10 J/cm2. Then the thickness of the deposition layer is determined by using the correlation coefficient method. Along the poloidal direction of HL-2A tokamak, the deposited impurity shows an inhomogeneous pattern, with the thickness of the deposition layer varying from 1.74 μm to 5.92 μm. Finally, the absolute depth distribution of each element is also quantitatively measured.

An approach for measurement of the magnetic field near the surface of plasma-facing components in tokamak by laser induced breakdown spectroscopy based on Zeeman effect

Laser-induced breakdown spectroscopy (LIBS) has been demonstrated to diagnose the surface element distribution of plasma-facing components (PFCS) in fusion devices. However, the magnetic field intensity and polarity near the wall surface change frequently and cannot be measured in real time, which will affect the analytical accuracy of LIBS results. The determination of the strength and polarity direction of the magnetic field near the surface will be conducive to the quantitative analysis of LIBS and provide valuable information for the distribution of the magnetic field near the surface of PFCs. In this work, the effects of magnetic fields on the characteristics of laser-induced Mo plasma, such as the ablation depth and mass, the spatio-temporal evolution behavior of spectrum and the plasma parameters, were first systematically investigated. The different phenomenon of continuum radiation, Mo I line and Mo II line under the magnetic field were mutually verified by optical emission spectroscopy and fast plasma imaging methods. Meanwhile, an approach for measurement of the magnetic field intensity and polarity near the surface of PFCS by LIBS method has been proposed and investigated. When the magnetic field polarity is changed, the spatial distribution profile of Mo spectrum will drift in the opposite direction affected by of the Lorentz force, which realizes the measurement of magnetic field polarity. Moreover, the splitting distance of Mo I line caused by Zeeman effect with the variable magnetic fields were preliminarily calculated. The experimental values of splitting distance agree well with the theoretical values that calculated by the known magnetic field strength. These results confirm the feasibility of measuring the magnetic field intensity and polarity of PFCs surface by LIBS approach.

Comparison of Mg/Ca concentration series from Patella depressa limpet shells using CF-LIBS and LA-ICP-MS

The elemental composition of marine mollusk shells can offer valuable information about environmental conditions experienced by a mollusk during its lifespan. Previous studies have shown significant correlations between Mg/Ca concentration ratios measured on biogenic carbonate of mollusk shells and sea surface temperature (SST). Here we propose the use of Laser-Induced Breakdown Spectroscopy (LIBS) and the validation of the Calibration-Free LIBS (CF-LIBS) approach for the rapid measurement and estimation of Mg/Ca molar concentration profiles within Patella depressa Pennant, 1777 limpet shells. To achieve these objectives, results derived from CF-LIBS methodology are compared with those obtained from an established analytical technique for this purpose, such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Concentration series obtained with both methodologies show defined temporal patterns and reflect the season-of-capture in each specimen. The results evidence a significant correlation (R2 = 0.63–0.81) between CF-LIBS and LA-ICP-MS Mg/Ca molar concentration profiles within four live-collected P. depressa shells. Averaged error for the molar concentration estimated with CF-LIBS was lower than 10% in every specimen. The comparison between the results obtained from two techniques used in this study has allowed us to demonstrate for the first time that Mg/Ca molar concentration measured in biogenic carbonates were accurately inferred using CF-LIBS technique. The CF-LIBS approach validation represents great potential for the rapid and large-scale paleoenvironmental and archaeological analysis of this mollusk species, which is frequently found in archaeological sites.

Increasing resolution in chemical mapping of geomaterials: From X-ray fluorescence to laser-induced breakdown spectroscopy

Laser-Induced Breakdown Spectroscopy (LIBS) micro-mapping is an important analytical tool for the study of geomaterials. In this work, this technique was applied, for the first time, to the analysis of alkali-activated materials and geopolymers, as well as rocks, mortars and bricks. The results obtained were compared with the ones obtained using Energy-Dispersive X-Ray Fluorescence (ED-XRF) macro-mapping and the advantages of the LIBS approach (speed, lateral and in-depth resolution, capability of light elements analysis) were highlighted.The issues associated with the quantitative determination of the samples' composition from the analysis of the LIBS spectra were also briefly discussed.

Qualitative and quantitative discrimination of major elements in Chitosan (natural polymer) using laser induced breakdown spectroscopy

In this work, Laser-Induced Breakdown Spectroscopy (LIBS) is used for qualitative and quantitative analysis of Chitosan samples (natural polymer). For qualitative analysis, plasma parameters are determined, while for quantitative analysis, the initial concentration of chitosan samples is calculated. It developed a plasma plume using a second harmonic (532 nm) laser pulses, which makes the Q-Switched Nd: YAG laser compatible with delay generators and computing electronics. The component elements and their corresponding concentrations are calculated based on the strongest emission lines of the element using the line intensity ratio method and the calibration-free LIBS approach. The results obtained by both methods are compared for the effectiveness of the algorithm.In the chitosan monomer (C6H11NO4)n, four major elements (hydrogen, carbon, nitrogen and oxygen) were detected and their quantities were calculated. In addition to investigating the physical behavior of plasma in the interaction of laser beams with materials, the plasma parameters (electron number density and plasma temperature) are determined by stark-broadening profile fitting and Boltzmann plot method, respectively. The results obtained show that the LIBS can be exploited for quantitative and standard analysis of industrial grade materials for better results in applications.

Three-dimensional topographic and multi-elemental mapping by unilateral-shift-subtracting confocal controlled LIBS microscopy

Laser induced breakdown spectroscopy (LIBS) is a promising analytical technique based on the interaction between laser and material, which can quantitatively analyse the composition and content of material from the perspective of spectroscopy. The element distribution of non-uniform samples, such as natural ore, can be obtained by pointwise scanning without pretreatment. LIBS excitation intensity is the highest near the focus, so low imaging speed and low focusing accuracy will lead to unreliable element maps. Hence, an ultrasensitive technique called unilateral-shift-subtracting confocal controlled LIBS microscopy (UCCLIBS) was prepared to rapidly acquire high spatial resolution multi-elemental maps of the sample surface, which utilizes a laser induced breakdown spectrometer attached to a unilateral-shift-subtracting confocal microscope. A surface axial focusing ability of approximately 18 nm under 20× objective lens with the N.A. value of 0.4 is obtained, which is more than two orders of magnitude higher than that of ever traditional LIBS approaches, and the inherent anti-drift capability is successfully realized. The chemometric method of principal component analysis (PCA) is applied to the multi-element analysis of agate ore, which improved the accuracy and efficiency of sample analysis. We show the multi-layer element map of a solid-state electrolyte with a tomographic resolution of 2.3 μm. With these excellent properties, the UCCLIBS might provide a new idea for the detection of three-dimensional elemental characterization of minerals and chemical materials.

Quantitative determination of antimony in archaeological bronze artefacts by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a reliable, fast and micro-destructive diagnostic method for qualitative and quantitative analysis of a variety of materials. In this paper, we report the results of quantitative determination of antimony in four archaeological bronze artefacts analyzed by means of LIBS. For the purpose of this study, an approach of multi-elemental quantitative LIBS analysis is proposed, based on the use of an element with known concentration as an internal standard and measurement of the spectral lines intensities of the internal standard and the element with unknown concentration. An important plasma parameter which is included in the quantitative analysis is the excitation temperature as determined by the Boltzmann plot method. The quantity of antimony in the bronze artefacts obtained by means of the proposed LIBS approach is between 1.49% and 3.13%.

Rapid geochemical imaging of rocks and minerals with handheld laser induced breakdown spectroscopy (LIBS)

Geochemical imaging is a powerful tool for unravelling the complex geological histories of rocks and minerals. However, its applications have until recently been restricted to geological research in a lab environment due to the cost and size of conventional instrumentation, long analysis times, and extensive sample preparation for some methods. Herein we present a rapid, qualitative geochemical imaging method for rocks and minerals using handheld LIBS. Analyses were completed directly on sawed drill core surfaces for a suite of kimberlite-hosted mantle xenoliths (Jericho and Muskox kimberlites, Nunavut, Canada). Semi-automated LIBS spectral processing following a new open-source workflow allows stitching of multiple small-area maps (each approximately 3 × 3 mm that take 2–3 min to complete) to produce cm-scale geochemical images of variably altered mantle xenolith samples (total data acquisition in 1–2 h). Replicate analyses of a ZnAl alloy reference material (NZA-1; CANMET) that were undertaken during standard-sample bracketing suggests that the relative standard deviation (RSD) is typically 15–20% for sum-normalized emission intensities above the estimated background. We demonstrate with open-source machine learning tools how qualitative LIBS spectral data can be converted to Feature-Of-Interest (FOI) maps to distinguish a variety of metasomatic and alteration features (e.g., Cr-diopside, kelyphite rims on pyrope garnet, and calcite veinlets) from the primary mantle mineralogy (e.g., olivine and orthopyroxene). Our results further demonstrate that the resolution of handheld LIBS-based geochemical imaging is sufficient to map veinlets and grain boundaries lined with metasomatic minerals. The LIBS approach is particularly sensitive for mapping the microscale distribution of elements with low atomic number (e.g., Li and Na). These light elements are difficult to detect at low concentrations with other handheld and field-portable technologies, but represent important geochemical tracers of hydrothermal and magmatic processes. Rapid LIBS mapping thus represents an emerging geochemical imaging tool for unravelling the complex geological history of rocks and minerals in the field with minimal to no sample preparation.

Quantification of surface contamination on optical glass via sensitivity-improved calibration-free laser-induced breakdown spectroscopy

We report quantitative analysis of manufacturing-induced trace contaminants of optical glass surfaces by laser-induced breakdown spectroscopy (LIBS). Therefore, spectra recorded with an echelle spectrometer coupled to a gated detector were analysed using a calibration-free LIBS approach based on the calculation of the spectral radiance of a plasma in local thermodynamic equilibrium. The measurements were carried out in experimental conditions that enable both accurate modelling of plasma emission and high sensitivity for trace element analysis. Depth-resolved measurements were performed by recording spectra for successive laser pulses applied to the same irradiation sites. Validated via inductively coupled plasma atomic emission spectroscopy for the bulk glass composition, the measurements evidence a surface contamination that originates from polishing during glass manufacturing. The measured penetration depths of the contaminants are discussed in the frame of the underlying mechanisms of surface contamination and related to the changes of the optical properties evidenced by ellipsometric measurements. Demonstrated here for optical glass, the sensitivity-improved calibration-free LIBS approach can be used to quantify contaminations of surfaces in all kind of technological applications.

Impact of microstructural properties on hardness of tungsten heavy alloy evaluated by stand-off LIBS after PSI plasma irradiation

The key issue in tokamak is change of physical properties of plasma facing materials, such as tungsten due to extreme conditions and long pulse operation. Practically, it is difficult to analyze hardness changes online through conventional methods. Hence, an online monitoring technique is much desired which measures hardness changes in fusion devices. In this study, laser induced breakdown spectroscopy (LIBS) is used as in-situ monitoring tool to measure hardness of tungsten heavy alloy (97W–2Ni–1Fe) samples after exposure to different irradiation of plasma ranging from 0.108 to 1.00 MW/m2. The exposure of PSI plasma beam is a key factor which give rise to pronounced change in crystallographic estimation, microstructural properties and surface hardness. The X–ray diffraction study revealed modification in the structure caused, by variation in the peak intensity, crystal size, dislocation line density and micro-strains upon plasma irradiation. The change in crystallographic measurements and surface hardness are well correlated with irradiated PSI power densities. Moreover, the hardness influence on LIBS intensity of tungsten heavy alloy (WHA) was carried out. The LIBS calibration curves were formed by utilizing the ratio of ionic to atomic line intensities of tungsten versus the Vickers hardness. The ratio of ionic to atomic spectral emission line intensity and plasma electron temperature (Te), significantly increases with hardness. The obtained Pearson correlation coefficient (R2) values (in case of calibration curve and plasma temperature) in measuring hardness of all investigated samples have good approximation which indicate the preciseness of LIBS approach. The achieved results in the present study by in-situ LIBS system confirmed its potential ability to estimate the hardness of WHA more efficient than other conventional method.

Laser-Induced breakdown spectroscopy (LIBS) for the analyses of faunal bones: Assembling of individuals and elemental quantification

Among the innumerable remains that appear in the archaeological sites, the faunal fossil remains are one of the most numerous. Different specialities study these fossil remains of fauna from different perspectives. Among them, the quantification of the remains is some of the most important information, since they allow us to estimate what species there are and what representativeness they can have. The problem is that the archaeological sites usually consist of several bones from different species and individuals. The minimum number of individuals (MNI) is usually used to estimate the representativeness of the species (e.g. there are 4 individuals of deer and 3 individuals of horses). The problem with this technique is that it does not allow to relate the remains that appear with each individual in a concrete way. Just the DNA analysis is necessary to reassemble the remains. However, the high cost and difficulty of implementation of DNA analysis do not allow performing a genetic study. In this paper, the combination of Laser-Induced Breakdown Spectroscopy (LIBS) and Neural Networks (NN) has been successfully implemented to discriminate and reassemble wild deer bones from different individuals. This is a step further from human bones classification and one step behind the archaeological bones classification. The elemental composition of bones provides enough information to get the correct discrimination of different individuals. The spectral correlation has exceeded 93 %. There have been no false positives and negatives. Also, the quantification of the different inorganic elements present in all bone samples has been achieved by the Calibration-Free LIBS (CF-LIBS) approach. Both approaches are different, NN is more qualitative and CF-LIBS, quantitative. Usually, chemometric methods are employed for the discrimination of samples, but it is an approach that requires a lot of LIBS spectra in order to perform the training, validation and test. In the case of CF-LIBS, only one spectrum with a certain degree of accumulation is necessary to obtain the elemental concentration. Thus, both approaches have been explored in this work. This fast analysis could allow archaeologist to perform a correct classification of individuals without performing several DNA´s analysis. This would save time and resources.

Spectral diagnosis of health hazardous toxins in face foundation powders using laser induced breakdown spectroscopy and inductively coupled plasma-optical emission spectroscopy (ICP-OES)

In this work, we applied laser-induced breakdown spectroscopy (LIBS) to estimate the amount of toxic heavy metals (Pb, Cr, Ni) in five different brands of face foundation powders available in the local market using standard calibration curve (CC)-LIBS approach. These samples contain toxic elements like lead, chromium, nickel which are highly carcinogens to cause eczematous and atopic dermatitis. The strongest atomic transition lines of lead (405.7 line), chromium (425.4 nm line), and nickel (336.9 nm line) were used as spectral markers to simultaneously detect these three heavy metals in face powder samples. The LIBS experimental parameters (delay time, laser energy, and focusing lens to target spacing) were optimized to enhance the signal to noise ratio in the resulting LIBS spectra. The consequence of self-absorption on the marker peaks used in the LIBS analysis was investigated and found to be insignificant. We calibrated our LIBS system for these three heavy metals, whose levels were found above the permissible limits. The face foundation powder used every day augments up to considerable exposure of heavy metals in the human body which could cause many skin disorders. Our LIBS quantitative results were also cross-validated by analysis using a standard analytical technique known as inductively coupled plasma-optical emission spectroscopy (ICP-OES). This study is highly significant due to the excessive use of cosmetic products especially face powder that could affect the health of millions of people around the globe.

Selection of molybdenum lines by quantitative analysis of molybdenum- zirconium-titanium alloy by CF-LIBS for future fusion applications

Molybdenum and its alloys have been chosen as substrate and support material for tungsten thin layers at special limiters and divertors parts of tokamak devices. These Molybdenum parts of the tokamak walls are used for mapping and quantification of material migration and redeposition. In this work, we used Laser Induced Breakdown Spectroscopy (LIBS) as a diagnostic method to analyse Mo-Zr-Ti alloy (TZM) under three different ambient conditions expected in a tokamak in between periods of plasma operation. LIBS spectra were measured under air atmosphere and under Argon and Nitrogen flow at the laser spot on the sample. The resulting plasma plume was created using Nd:YAG (1064 nm) laser operating at the fourth harmonic frequency (266 nm). Atomic and ionic spectral lines of Mo, Ti and Zr were selected from spectra and used for analysis. The evolution of plasma parameters – electron density (ne) and electron temperature (Te) - has been observed by choosing different gate windows and delays relative to the laser pulse. Finally, the elemental concentration of the TZM sample has been calculated by the calibration free LIBS approach. The results are showing that most suitable conditions for elemental analysis are gate delay and gate width equal to 750, 1000, 1500 ns respectively, where we observed similar elementary concentrations in all three conditions.

Analysis of Soil by Magnetic Field Assisted Calibration-Free Laser Induced Breakdown Spectroscopy (CF-LIBS) and Laser Ablation – Time-of-Flight Mass Spectrometry (LA-TOF-MS)

The qualitative and quantitative analysis of soil samples collected from Sialkot, Pakistan (which contains leather industrial plants), has been performed using laser-induced breakdown spectroscopy (LIBS) and laser ablation time of flight mass spectrometry (LA-TOF-MS). The focused beam of a Q-switched Nd: YAG laser (532 nm) was used to ablate the soil samples in air at atmospheric pressure. The optical emission spectra demonstrate the presence of the spectral lines of Si, Fe, Al, Ca, Ti, K, Cr, Mg, Na, Ba, and Li in all of the samples. The emission lines intensities, electron number densities, and excitation temperatures were significantly enhanced in the presence of an external 0.3 T magnetic field applied perpendicular to the plasma plume. A maximum enhancement factor of approximately 8 was observed in the emission intensity. The emergence of several additional lines has also been detected using the magnetic field-assisted LIBS approach. The elemental composition determined using calibration-free laser-induced breakdown spectroscopy (CF-LIBS), with and without magnetic field, reveals that the external magnetic field only adjusts the laser-generated plasma dynamics without affecting the quantitative analysis of the samples. Importantly, the toxic and heavy elements such as chromium and barium were detected and quantified in all of the soil samples by both of these techniques. The variations in the compositional analysis using CF-LIBS with and without the applied magnetic field and LA-TOF-MS were less than 10%.

Analytical Approach of Laser-Induced Breakdown Spectroscopy to Detect Elemental Profile of Medicinal Plants Leaves

Laser ablation chemical and spectroscopic studies of Calotropis procera, Chenopodium ambrosioides, and Nerium indicum leaves was performed using 1064 nm Nd: YAG laser in air at different pressure and time delay. These medicinal plant’s leaves are used by local people for different diseases. The knowledge of medicinal and toxic metals in these plants is very important. We have presented time-resolved studies of different elements and how their lives change with different delay time. C, H, Si, Al, Fe, Cu, Ca, Mg, Na, K, N, O, Sr and Ba have been detected in all the three samples with a molecular form of Carbon and Nitrogen band. We have detected C, H, N, and O as a major element while, Fe, Cu, Mg, K and Ca as essential medicinal metals with other trace elements such as Si, Sr, Al and Ba in all the three plants leaves. We present 1 µs delay time is the best time for elements lifetime in time resolved studies. The behaviour of intensity with different pressures was also studied and it was concluded that 7 torr was the best pressure for the maximum value of intensity. In particular, the electron density and the temperatures of the plasma were reported. The temperature was calculated from the well-known Boltzmann plot method and electron density was estimated from the stark broadened profile of the Hα line.

Laser-induced plasma image velocimetry

A novel velocimetry method is proposed for point velocity measurement, which is based on tracking a laser-induced plasma in a flow. The plasma’s behaviour is first analysed spatially, temporally and spectrally in quiescent air. The dependence of this technique on the delay time between subsequent plasma images and the processing methods are described. It is found that, for optimized operation of the technique in a turbulent air jet (exit diameter 10.0 mm from a 480 mm long pipe; with an averaged velocity of 50 m/s at the jet exit resulting in Reynolds number of 34,000) with 100 µs time delay between plasma images, the systematic and random components of the velocity uncertainty are − 0.51 m/s and ± 3.6 m/s along the laser beam direction, and 1.25 m/s and ± 0.86 m/s along other directions perpendicular to the laser beam. These uncertainties are mainly caused by the asymmetric laser energy deposition during the formation of plasma, and the associated spatial resolution (in this realisation of the instrument) of 5 mm. The mean velocity measurements in the turbulent air jet flow are consistent with the reported flow behaviour in the literature for mean velocity: the turbulent intensity of axial velocity fluctuations is comparable to those in the literature but difference arises due to the limited spatial resolution. This velocimetry method is an alternative to traditional tracer-based velocimetry methods, because it does not require ‘seeding’ of particles or other substances in the flow. It also has the ability to measure local gas mixture composition, using laser-induced breakdown spectroscopy approach, simultaneously with flow velocity, but this aspect is not explored in the current study.Graphical abstractConcept of Laser-Induced Plasma Image Velocimetry (LIPIV) applied to a turbulent jet flow. The LIPIV technique measures the flow velocity vector by using the temporal displacement of the laser-induced plasma in a flowing fluid. For this reason, two sequential images of the plasma with time delay Δt are used.

Application of Laser Induced Breakdown in Air in Conjunction with Atomic Absorption Spectroscopy for Detection of Trace Elements in Fennel Seeds

A robust approach of laser-induced breakdown spectroscopy (LIBS) in ambient air has been employed to investigate concentration of the trace elements in fennel seeds (saunf) via generation of plasma through the second harmonic of solid state Nd: YAG pulsed laser 532 nm. Spectral emissions of saunf plasma were acquired with resolution of 0.06 nm in spectral range of 200–720 nm. The experimental determination showed the existence of elements namely, Ca, Al, K, Fe, S, P, Mg, Mn, Sr, Na, and Zn in the sample. However, no toxic elements such as Pb, Cr etc. were perceived. The relative concentrations of detected elements were measured through the intensity of the strongest peak, intensities of every emission from every specie, and calibration free (CF)-LIBS. To indorse the experimental determinations of LIBS, a comparative study was carried out with the outcomes of atomic absorption spectroscopy (AAS). The results of LIBS and AAS were compared by the statistical treatment.

Application of a laser-induced breakdown spectroscopy handheld instrument to the diagnostic analysis of stone monuments

Laser-induced breakdown spectroscopy (LIBS) has been in use for decades, but only recently the technique has progressed so to allow the construction of efficient handheld, self-contained commercial instruments featuring a large range of capabilities. In particular, the development of portable handheld instruments able to perform non-invasive, spatially resolved, multielement, in-situ analysis has provided an impressive impulse to the scientific investigation of cultural heritage materials. In this work, the design of a handheld LIBS instrument and the first test measurements performed on a fragment of a sedimentary rock monument are presented. A full broadband LIBS emission spectrum with a point and shoot operation was recorded directly within few seconds, so providing information on the elements present in the weathered layer in comparison to the stone surface. Further, the Calibration Free (CF)-LIBS approach was used to test the possibility to obtain a suitable quantitative composition of the main elements present in the sample.