Double-pulse Laser-induced Breakdown Spectroscopy Research Articles

Signal Improvement for Underwater Measurement of Metal Samples Using Collinear Long-Short Double-Pulse Laser Induced Breakdown Spectroscopy

A collinear long-short double-pulse laser induced breakdown spectroscopy (LS-DP-LIBS) is employed to detect the underwater metal samples. The emission spectra, time-resolved signal, plasma images and sound characteristics of plasma shockwave are experimentally investigated in this work. The results show that the underwater signal of Al, Cu and Fe spectral lines are significantly improved by collinear LS-DP-LIBS with inter-pulse delay of 35 us. The mechanism of the signal improvement is considered to be the pre irradiation effect of long pulse laser beam. In the collinear LS-DP-LIBS method, the long pulse firstly generates a cavitation bubble in water and provides the gaseous environment. Then the short pulse generates the plasma from sample surface. The present experiments show that the collinear LS-DP-LIBS method has acquired significantly signal improvement in underwater measurement of metal samples. This new method has great potential in deep-sea exploration using LIBS.

Spectral Characterization of Collinear Double-Pulse Laser Induced Breakdown Spectroscopy (DP-LIBS) for the Analysis of the Chinese Traditional Medicine Artemisia annua

A collinear dual-pulse laser induced breakdown spectroscopy (DP-LIBS) method was employed to analyze Chinese traditional medicine Artemisia annua. The spectral intensities and signal-to-background ratios of magnesium (II) 279.54 nm, CN 388.29 nm, calcium (II) 393.37 nm, and iron (II) 404.27 nm were used to evaluate the optical emission characteristics of A. annua induced by DP-LIBS. The temporal evolution characteristics, inter-pulse time, and laser energy values were optimized. In particular, the electron density and the temperatures of the plasma were reported as functions of the delay time. The results showed that the DP-LIBS had stronger intensity and better accuracy compared to single-pulse (SP) LIBS. The enhancement factors obtained using DP-LIBS for Mg, CN, Ca, and Fe were 7.2, 8.9, 13.8, and 3.4, respectively. This study provides important information about A. annua.

Fraunhofer-type signal for underwater measurement of copper sample using collinear long-short double-pulse laser-induced breakdown spectroscopy

The collinear long-short double-pulse laser-induced breakdown spectroscopy (long-shrot DP-LIBS) is used to detect the underwater copper sample. Fraunhofer-type signal is acquired with very short gate delay parameter, which is the first time to be reported that the collinear long-short DP-LIBS can generate Fraunhofer-type signal from underwater target. It is found that the early structure of underwater plasma is similar to the solar structure. According to the plasma image of early stage, a cold shell with low emission intensity is wrapped around a hot core with strong emission intensity. During early period, the continuum radiation from the hot core is absorbed by the copper atoms in plasma edge, causing Fraunhofer-type absorption at Cu I 324.754 nm and Cu I 327.396 nm. The experimental results show that the absorption intensity of Fraunhofer-type lines possesses a well signal stability in early stage. RSD% of signal is 1.5% with 10 ns delays and 5.3% with 30 ns delays at Cu I 324.754 nm, and RSD% is 2.7% with 10 ns delays and 3.3% with 30 ns delays at Cu I 327.396 nm. The present results sugget that the Fraunhofer-type signal generated by collinear long-short DP-LIBS is possible to be used for further underwater quantitative measurement.

Concentric multipass cell enhanced double-pulse laser-induced breakdown spectroscopy for sensitive elemental analysis

Although double-pulse laser-induced breakdown spectroscopy (DP-LIBS) is regarded as a promising technique in trace element analysis, its limit of detection (LOD) is not sufficient for some applications. The enhancement of spectral signal is the key to further improve the sensitivity of DP-LIBS. To further increase the sensitivity of DP-LIBS, a concentric multipass cell (CMC) enhanced DP-LIBS (CMC-DP-LIBS) technique is proposed for the first time, which makes full use of the energy of reheating laser by multi-reflection in CMC to enhance the spectral signal and lower LOD. 2.3 times signal enhancement of Mn I 403.08 nm line and 2.3 times decrease of LOD of Mn on the surface of zinc bulk compared with traditional orthogonal reheating DP-LIBS were attained. The signal enhancement factor can reach to 3.6 theoretically with the increase of reflectivity and the sizes of mirrors of CMC. This CMC-DP-LIBS provides a new approach to further improve the sensitivity of DP-LIBS and promotes its application in trace element detection.

Investigating double pulse nanoparticle enhanced laser induced breakdown spectroscopy

Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal, involving peculiar experimental configurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the LIBS performances; in particular, the Nanoparticle-Enhanced LIBS (NELIBS) methodology uses a deposition of metal nanoparticles (NPs) on the sample to greatly increase the emission of the LIBS plasma.In this work, we investigate the possibility of combining, for the first time, DP-LIBS with NELIBS. The chosen set-up uses two parallel non-collinear laser pulses to ensure the activation of NPs during both pulses, while maintaining the low-pressure environment typical of DP-LIBS. The two laser beams are spatially separated so that the second beam is focused within the shock wave generated by the first one. This configuration allows the exploitation of the combined enhancement of both DP-LIBS and NELIBS.Several tests on copper targets have been performed to determine the best set-up for the maximum magnitude of the signal enhancement by adjusting different parameters such as pulse energies and offset distances. Commercially available silver NPs and NPs prepared by pulsed laser ablation in liquid have been tested and their performances compared with standard DP-LIBS.

Carbon detection in solid and liquid steel samples using ultraviolet long-short double pulse laser-induced breakdown spectroscopy

An ultraviolet long-short double pulse laser-induced breakdown spectroscopy (UV LS-DP-LIBS) system is employed to detect the carbon element in solid and liquid steel samples. The important issues for the industrial application of LIBS are investigated in this work, which include the carbon excitation in steel, the influences of CO2, the quantitative analysis and the escape phenomenon of carbon. It is found that the CO2 in air can also be involved to the plasma generation and emits the carbon specific spectral lines. The strong emission line at C I 193.091 nm can be observed when the sample is placed in the gas atmosphere with CO2. It is also found that the carbon signal generated from liquid steel is continuously decreasing after the sample is molten. The experimental investigation demonstrates that the influences of O2 cause the carbon escape phenomenon in liquid steel, which should be fully considered for the industrial application of LIBS.

Evaluation of analytical performance of double pulse laser-induced breakdown spectroscopy for the detection of rare earth elements

Double pulse laser-induced breakdown spectroscopy (DP-LIBS) in collinear configuration was demonstrated to enhance the signal intensity of three rare earth elements (REEs), Eu, Gd, Pr, and Y (Yttrium is included because of its similar chemical properties and occurrence in similar deposits as REE). Significant enhancement in spectral signals of all elements was observed with an aid of second laser. Two laser pulses of 1064 nm wavelength were employed in collinear geometry on the Pr2O3, Eu2O3, Gd2O3, and Y2O3 pellets to obtain emission spectra. For selected strong emission lines of Eu and Gd signal enhancement was found to be 3–7-fold and that for Y and Pr lines was observed to be 3–13-fold compared to single-pulse laser-induced breakdown spectroscopy (SP-LIBS). Role of inter-pulse delay between two pulses in DP-LIBS was found to be very crucial. While comparing selected ionic and neutral lines, ionic lines were found to have larger signal enhancement in DP-LIBS at the experimental conditions used in this study.

Study of material ablation and plasma radiation in double-pulse laser induced breakdown spectroscopy at different delay times: Modeling and numerical simulation

A one-dimensional numerical model is presented on a copper sample to investigate double-pulse laser induced breakdown spectroscopy (DP-LIBS). The effect of the inter-pulse delay time on the material ablation, plasma homogeneity, and signal enhancement is examined. The dynamics of laser ablation, plume expansion, plasma formation, and plasma radiation of the ionized and neutral atoms in the presence of helium background gas at a pressure of 1 atm are studied. A heat conduction equation is solved in the sample and is coupled to the fluid dynamic equations through the Knudsen layer relations. Saha-Eggert equations are utilized to investigate the plasma formation. The influence of plasma shielding, due to the photoionization and inverse bremsstrahlung processes, is considered. Continuous radiation, bremsstrahlung and recombination radiations, and spectral emissions of the plasma are examined. The optimum inter-pulse delay time for maximizing the neutral and ionized spectral emissions is determined. The results reveal that the ablation rate in DP-LIBS is significantly higher than that of single pulse laser induced breakdown spectroscopy (SP-LIBS) and reaches its maximum at an optimum inter-pulse delay time due to the decrease in the recondensation of the ablated plume. Furthermore, it is demonstrated that in DP-LIBS, the ablation profile is smoother and its continuous radiation decreases much earlier than that of SP-LIBS. Although the double-pulse mode improves the signal to background ratio, it leads to more inhomogeneity in the plasma.

Enhanced optical emission in laser-induced breakdown spectroscopy by combining femtosecond and nanosecond laser pulses

The role of inter-pulse delay time in laser-induced Cu plasma with femtosecond and nanosecond double-pulse irradiation had been investigated by optical emission spectroscopy. The experimental results showed that a significant enhancement effect in the atomic line emission was observed by changing the inter-pulse delay time. The spectral intensity of Cu plasma produced by a femtosecond + nanosecond double-pulse was higher than that produced by a nanosecond + femtosecond dual-pulse. That is to say, the shorter laser pulse (femtosecond) was efficient in coupling to the sample and the longer laser pulse (nanosecond) was suitable for re-exciting the produced plasma. In addition, the corresponding plasma temperature and electron density were also calculated. The plasma temperature in the case of femtosecond + nanosecond was lower than that in the case of nanosecond + femtosecond, while the electron density in the case of femtosecond + nanosecond was higher than that in the case of nanosecond + femtosecond. This study is helpful for the research on sample detection using femtosecond and nanosecond double-pulse laser-induced breakdown spectroscopy.

Correction: Micro-destructive analysis with high sensitivity using double-pulse resonant laser-induced breakdown spectroscopy

Correction for ‘Micro-destructive analysis with high sensitivity using double-pulse resonant laser-induced breakdown spectroscopy’ by Zhiyang Tang et al., J. Anal. At. Spectrom., 2019, 34, 1198–1204, DOI: 10.1039/C9JA00072K.

Accurate sulfur determination of coal using double-pulse laser-induced breakdown spectroscopy

A helium atmosphere combined with DP-LIBS was presented to enhance the SNR and spectral intensity of S in coal, and weaken the spectral interference from O I 926.6 nm, to achieve high accuracy and sensitivity detection.

Spatiotemporal and spectroscopic investigations of the secondary plasma generated during double-pulse laser-induced breakdown in bulk water

Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) has been demonstrated to enable efficient elemental analysis of bulk water.

Triple-pulse LIBS: laser-induced breakdown spectroscopy signal enhancement by combination of pre-ablation and re-heating laser pulses

The goal of this work is to examine the effect of a third additional laser pulse on orthogonal double-pulse laser-induced breakdown spectroscopy (DP LIBS).

Laser-fluence dependence of signal enhancement in femtosecond double-pulse laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) based on femtosecond laser pulses has widely been used for analyzing chemical elements in samples. In this research, we achieved the double-pulse operation with a two-polarizer configuration, and the signal enhancement factor of 4–15 was observed as compared with the single pulse LIBS scheme. It is found that with the change in interpulse delay time between 0 and 150 ps, the laser-fluence dependence of the LIBS signal enhancement can be classified into three types that are characterized by the different behavior of linear and quadratic intensity increase, followed by the intensity saturation. Such different responses are presumably ascribable to the mechanisms of electron-ion relaxation and plasma reheating. Also, different behavior is seen for the signal enhancement with different laser intensity and beam diameter while the laser fluence is kept constant. This indicates that generally, the use of a larger beam diameter is recommended for increasing the signal enhancement factor.

Quantitative analysis of Pb in soil by femtosecond-nanosecond double-pulse laser-induced breakdown spectroscopy

The effects of inter-pulse delay on the quantitative analysis of femtosecond-nanosecond double-pulsed laser-induced breakdown spectroscopy (fs-ns DP-LIBS) for assessing Pb in soil have been systematically studied in this work. A femtosecond pulse laser was focused to produce a filament, which was used to ablate the soil sample and produce an appreciable amount of aerosol particles ejected from the soil surface at a low density. Scattering images of the soil particles ejected from the soil surface were obtained, and the soil particles were found to have a delay of 800 µs. After an inter-pulse delay, a nanosecond Nd:YAG laser re-ablated the soil particles and obtained a spectral enhancement and a narrow line width. The quantitative analysis based on DP-LIBS for Pb in soil was strongly dependent on the inter-pulse delay time. With an inter-pulse delay time of 10 µs for DP-LIBS, the R-square factor (R2), relative standard deviation (RSD), root mean square error of cross-validation (RMSECV), and limit of detection (LOD) were 99.42%, 2.99%, 0.42 wt%, and 8.13 mg/kg, respectively. These findings demonstrate that DP-LIBS can be applied as an efficient spectroscopic tool to improve the quantitative analysis of Pb heavy metal in soil.

Study of signal enhancement in collinear femtosecond-nanosecond double-pulse laser-induced breakdown spectroscopy

The study of spectral emission intensity on femtosecond-nanosecond double-pulse laser-induced breakdown spectroscopy with collinear configuration (fs and ns DP-LIBS collinear configuration) was presented. The experiment was carried out using silicon sample irradiated by a femtosecond laser beam and a nanosecond laser beam in air. In order to explore the advantages of the fs-ns DP-LIBS collinear configuration, the experiments of femtosecond SP-LIBS and nanosecond SP-LIBS were also investigated for the same silicon sample. The experimental results indicated that the femtosecond laser pulse is efficient in coupling to the sample and the nanosecond laser pulse is suitable for re-heating the produced plasma. In the meantime, the fs-ns DP-LIBS collinear configuration can be considered as an efficient technique for enhancing the spectral emission intensity in LIBS.

Shock Waves in Laser-Induced Plasmas

The production of a plasma by a pulsed laser beam in solids, liquids or gas is often associated with the generation of a strong shock wave, which can be studied and interpreted in the framework of the theory of strong explosion. In this review, we will briefly present a theoretical interpretation of the physical mechanisms of laser-generated shock waves. After that, we will discuss how the study of the dynamics of the laser-induced shock wave can be used for obtaining useful information about the laser–target interaction (for example, the energy delivered by the laser on the target material) or on the physical properties of the target itself (hardness). Finally, we will focus the discussion on how the laser-induced shock wave can be exploited in analytical applications of Laser-Induced Plasmas as, for example, in Double-Pulse Laser-Induced Breakdown Spectroscopy experiments.

Emission spectroscopy of long cylindrical laser spark with additional coaxial excitation

Low intensity lines of elements with high excitation potentials, especially non-metals, is one of the main problems of laser-induced breakdown spectroscopy (LIBS). To our knowledge, we report the first combination of long spark produced by a cylindrical lens with an additional orthogonal excitation along the long axis. We studied temporal evolution of the plasma parameters at delays in the range of 100 to 500 ns and inter-pulse delays of 600 to 1800 ns. This variant of double pulse LIBS leads to the formation of a rather large (approx. 14 mm length) and hot laser-induced plasma, (2.0–3.8) × 104 K, with a relatively low electron density, (2–8) × 1017 cm−3. Our analysis reveal that the proposed optical configuration provides the optimal conditions for observing ionic lines with high excitation potentials in comparison with the conventional LIBS arrangement.

溶液中Ba元素的水下单脉冲与正交双脉冲LIBS的比较研究

溶液中Ba元素的水下单脉冲与正交双脉冲LIBS的比较研究

Quantitative analysis of Cu and Pb in <i>Coptidis</i> by reheated double pulse laser induced breakdown spectroscopy

<i>Coptidis</i> plays an important role in the field of traditional Chinese medicine. However, it is easily polluted by heavy metals in environment (water and soil), and thus can affect human health. In order to detect the heavy metal elements Cu and Pb in <i>Coptidis</i>, which was purchased from the Chinese herbal medicine market in Chongqing, the reheated double-pulse laser-induced breakdown spectroscopy (RDP-LIBS) is investigated. In order to reduce the experimental error caused by the irregular shape, it is necessary to pretreat the <i>Coptidis</i> samples prior to the determination step. The <i>Coptidis</i> samples are dried, milled, and sieved to form thin cylindrical tablets each with a diameter of 13 mm and thickness of 2 mm, which are formed under a mechanical press of 10 MPa for 2 min. The influences of the main experimental parameters, such as double-pulse LIBS detection delay, double-pulse LIBS laser energy, and double-pulse LIBS pulse interval are optimized. According to the LIBS signal intensity and signal-to-background ratio, the optimal laser energy set of the characteristic line Cu I (324.46 nm) covers <i>E</i><sub>1</sub> = 15 mJ and <i>E</i><sub>2</sub> = 35 mJ, and the pulse interval and detection delay time are 1.4 μs and 1.5 μs respectively; the laser energy set of Pb I (405.78 nm) also covers <i>E</i><sub>1</sub> = 15 mJ and <i>E</i><sub>2</sub> = 35 mJ, and the pulse interval and detection delay time are 1.6 μs and 1.7 μs, respectively. Comparing with the scenarios of single-pulse laser-induced breakdown spectroscopy, it can be seen that the spectral intensity of Cu I (324.46 nm) increases from 5779 counts to 12749 counts, i.e. it increases about 2.2 times; the spectral intensity of Pb I (405.78 nm) characteristic line increases from 4703 counts to 15838 counts, i.e. it increases about 3.3 times. It is shown that the second laser pulse re-excites the plasma which is generated by the first laser pulse, thus making the plasma emission spectrum stronger. The detection performances of heavy metal elements in Chinese medicinal materials are evaluated by RDP-LIBS and SP-LIBS. The results show that the detection limit of Cu decreases from 5.13 mg/kg to 1.91 mg/kg, and the detection limit of Pb decreases from 10.87 mg/kg to 3.03 mg/kg. There was observed a noticeable difference in the limit of detection between Cu and Pb, which meets the requirements of the Green Industry Standard for Import and Export of Medicinal Plants. Moreover, the linear curve fitting degree of RDP-LIBS is higher than that of SP-LIBS, which indicates that the RDP-LIBS technology has better detection performance in Chinese herbal medicine.