Laser-Induced Breakdown Spectroscopy LIBS

This popular technique is used for the analysis of solid or liquid surfaces. Its technique can be summarized as follows (Fig. 1.60) A pulsed laser with high peak power is focussed onto the surface and evaporates electrons, neutral atoms or molecules and ions. The emitted particles form a hot plasma (up to 100,000 K), which expands and cools down, reaching soon thermal equilibrium at about 10,000 K. 

With a second laser electronic transitions in the neutral atoms or the ions are excited and the laser-induced fluorescence is monitored for specific known excitation lines. With a time gate in the detector system the spectra can be taken at different times and therefore different temperatures of the expanding plasma. The intensity of the LIF gives information about the atomic composition of the evaporated material and the abundance of the excited species, if the transition probabilities are known [198, 199]. The sensitivity of the technique depends on the peak intensity and the pulse duration of the excitation laser pulses. Typical laser pulse widths range from nanoseconds to picoseconds. Recently also femtosecond lasers have been used. Since only a tiny amount of material (nanograms to picograms) is evaporated the sample is not essentially damaged by this purely optical analysis [200]. 

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Anglos, D. (2001), Laser-induced breakdown spectroscopy (LIBS) in art and archaeology, Appl. Spectrosc. 55(6), 186A-205A. 

Vukjovic et al.199 recently proposed a simple, fast, sensitive, and low-cost procedure based on solid phase spectrophotometric (SPS) and multicomponent analysis by multiple linear regression (MA) to determine traces of heavy metals in pharmaceuticals. Other spectroscopic techniques employed for high-throughput pharmaceutical analysis include laser-induced breakdown spectroscopy (LIBS),200 201 fluorescence spectroscopy,202 204 diffusive reflectance spectroscopy,205 laser-based nephelometry,206 automated polarized light microscopy,207 and laser diffraction and image analysis.208... 

The emerging analytical technique of laser-induced breakdown spectroscopy (LIBS) is a simple atomic emission spectroscopy technique that has the potential for real-time man-portable chemical analysis in the field. Because LIBS is simultaneously sensitive to all elements, a single laser shot can be used to record the broadband emission spectra, which provides a chemical fingerprint of a material. 

Laser heating, case hardening by, 16 200 Laser heterodyne radiometry, 23 142 Laser-induced breakdown spectroscopy (LIBS), archaeological materials, 5 743 Laser-induced EDC cracking, 25 646 Laser-induced fluorescence, 23 127 Laser-induced fluorescence imaging, application in combinatorial chemistry, 7 404... 

Abstract world class unconformity-related U deposits occur in the Proterozoic McArthur Basin (Northern Territory, Australia) and Athabasca Basin (Saskatchewan, Canada). Widespread pre-to post-ore silicifications in the vicinity of the deposits, allow proper observation of paragenetically well-characterized fluid inclusions. We used a combination of microthermometry, Raman microspectroscopy and Laser Induced Breakdown Spectroscopy (LIBS), to establish the physical-chemical characteristics of the main fluids having circulated at the time of U mineralization. The deduced salinities, cation ratios (Na/Ca, Na/Mg) and P-T conditions, led to the detailed characterization of a NaCI-rich brine, a CaCl2-rich brine and a low-salinity fluid, and to the identification of mixing processes that appear to be key factors for U mineralization. 

Time-Resolved Laser-Induced Breakdown Spectroscopy (LIBS)... 

Three techniques with spatially resolved information capabilities have been selected here for some further explanation EPXMA, laser-induced breakdown spectroscopy (LIBS) and glow discharge optical emission spectrometry (GD-OES). Figure 1.15 summarises the lateral and depth resolution provided by the techniques described in this section. It is worth noting that the closer to the bottom left corner the technique is located, the higher (and so better) is the depth resolution. 

PRINTING PROCESSES] (Vol 20) Laser-induced breakdown spectroscopy (libs)... 

Fig. 8. Single-shot laser-induced breakdown spectroscopy (LIBS) spectrum of type I plastic collected from a...

Fig. 9. Single-shot laser-induced breakdown spectroscopy (LIBS) spectra collected with man-portable LIBS system of (a) RDX residue on aluminum under argon, (b) RDX on aluminum in ambient atmosphere, and (c) plain aluminum in ambient atmosphere. Carbon (C), Hydrogen (H), Nitrogen (N), and Oxygen (O) are shown...

Fig. 11. Comparison of laser-induced breakdown spectroscopy (LIBS) spectra of RDX using die double-pulse configuration and the single-pulse configuration. Two 160-mJ pulses were separated by 2jjls for die doublepulse spectrum. One 320-mJ pulse was used to collect die single-pulse spectrum. The O to N intensity ratio for die double pulse and the single pulse is 4 and 2, respectively.

Another micro-destructive technique is laser-induced breakdown spectroscopy (LIBS) which is used to analyse the paint layers. Nanosecond laser pulses vaporise a small amount of material from the surface of the painting and the amounts so lost are only 50 billionths of a gram and too small to be seen with the naked eye. The vapour passes between two high-voltage electrodes which excite the atoms and these then emit a pattern of light energy bands which identify the elements. LIBS together with Raman spectroscopy has been used to examine Russian icons which are multilayered. 

Mouget, Y., Gossehn, P.,Tourigny, M, and B echard, S. (2003), Three-dimensional analyses of tablet content and film coating uniformity by laser-induced breakdown spectroscopy (LIBS), Am. Lab., 35, 20-22. 

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