LIBS-Raman

2 Raman-Laser Induced Timed Resolved Luminescence 

Simultaneously detected LIBS and Raman signals of quartz (a) and calcite (b) received with short timing set for Raman and long timing set for LIBS 

These differences lead to trade-off issues that will be considered in the proper design of a combined system. 

Recently the compact time-resolved (TR) Raman, and fluorescence spectrometers suitable for planetary exploration under NASA s Mars Instrument Development Program have been developed (Sharma et al. 2012). The compact Raman and fluorescence spectrometers consist of custom miniature spectrographs based on volume holographic gratings, and custom miniature intensified CCD cameras. Using a small frequency-doubled Nd YAG pulsed laser (35 mJ/pulse, 20 Hz) and 50 mm camera lens, TR Raman and laser-induced fluorescence spectra of minerals from rare-earths and transition-metal ions in time domain and in the spectral range of 400-800 nm can be measured. 

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Photon Vis light imaging microspectroscopy, mi-crospectrolluorimetry, LIBS, Raman and FTIR SEM-EDX, EPMA ... 

Fig. 8.52 (a-c) Gated Raman spectra with excitation by 532 nm of alite, CaO and MgO S.3.9.2 LIBS-Raman for Online Mineral Analysis... 

Burgio, L., R. J. H. Clark, T. Stratoudaki, M. Doulgeridis, and D. Anglos (2000), Pigment identification in painted artworks A dual analytical approach employing LIBS (laser-induced breakdown spectroscopy) and Raman microscopy, Appl. Spectrosc. 54(4), 463-469. 

As an example of the application of joint micro-LIBS and micro-Raman analysis on actual samples, results are reported on the study of a small fragment (less than 1 mm2) of the S.Antonio Abate , a wooden painted artwork decorating the Arciconfratemita della Misericordia in Siena, attributed to the Renaissance Italian artist Domenico di Pace, also known as II Beccafumi (Montaperti 1486 - Siena 1551). The sample, whose dimensions were relatively small (less than 1 mm2), was given by Opificio delle Pietre Dure di Firenze (OPD) to the Department of Chemistry of Pisa University, where it was going to be analysed for the presence of lakes in the... 

Since LIBS analysis doesn t give information about the molecular composition of the pigments, a micro-Raman analysis was performed for an exact characterization of the sample. 

Bicchieri M., Nardone M., Russo P.A., Sodo A., Corsi M., Cristoforetti G., Palleschi V., Salvetti A., Tognoni E., Characterization of azurite and lazurite based pigments by LIBS and micro-Raman spectroscopy, Spectrochim. Acta B 2001 56 915-922. 

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. 

Derome D., Cathelineau M., Fabre C., Boiron M.-C., Banks D.A., Lhomme T., Cuney M. 2007. Paleo-fluid composition determined from individual fluid inclusions by Raman and LIBS Application to mid-proterozoic evaporitic Na-Ca brines (Alligator Rivers Uranium Field, northern territories Australia). Chemical Geology 237(3-4), 240-254. 

A minerals analysis at a distance of 10 m has been done with a modified Raman system to collect LIBS data, thus obtaining quantitative values for cation... 

Luminescence and LIBS techniques may b e used simultaneously with the same basic equipment. This property may be effectively used in minerals sorting. Besides that, other methods such as Raman and SHG may be effective. 

Working with titanite, one sample has been found with luminescent behavior strongly different from the others. Suspicion was raised that its identification is not correct. In order to check it, LIBS and Raman data have been received from the same area where liuninescence spectra were determined. Figure 9. la demonstrates that breakdown spectra of titanite are really characterized by the group of UV fines at 300 nm of Ti and by many fines of Ca, the strongest ones at 393 and 396 nm. Nevertheless, such fines are absent in the LIBS of the suspicious sample, where only a strong fine of Na presents at 589 nm and its Raman spectrum (Fig. 9.1c) is totally different from those of titanite (Fig. 9.1b). Subsequent EDX and XRD analyses enabled us to identify this mineral as catapleite. 

Another example is a mineral named nasonite, which was not suspicious because of its luminescent properties, but gave unexpected results after routine LIBS checking (Fig. 9.2a), where the characteristic fines of Pb were absent, while the emission fines of Ca and Na were very strong. The Raman spectrum (Fig. 9.2b) was also different from those of nasonite. Subsequent analyses by EDX and XRD methods revealed that it is a mixture of two minerals prehnite and pectolite. 

Table 9.1. Luminescence, Raman and LIBS parameters of several gem stones...

Fig. 9.3. a-f Raman spectra and LIBS of several precious stones... 

Because chemical and structural properties of natural and artificial gems are very similar in this case, the possibilities of Raman and LIBS methods are rather limited. It was found that another laser-based techniques could be very effective for rapid spectroscopic discrimination between natural and synthetic emeralds, rubies, and alexandrite (Armstrong et al. 2000a,b). The first one is DRIFTS (Diffuse Reflectance Fourier Transformed Infra-Red Spectroscopy)... 

The possibilities of time-resolved laser based spectroscopies have been demonstrated, combining such techniques as luminescence, Raman, breakdown and second-harmonic generation. Radiometric sorting of minerals using LIBS was patented and apparatus for evaluation of phosphate rocks with elevated dolomite content has been developed and constructed. 

In addition to the IR, Raman and LIBS methods previously discussed, a number of other laser-based methods for explosives detection have been developed over the years. The following section briefly describes the ultraviolet and visible (UV/vis) absorption spectra of EM and discusses the techniques of laser desorption (LD), PF with detection through resonance-enhanced multiphoton ionization (REMPI) or laser-induced fluorescence (LIF), photoacoustic spectroscopy (PAS), variations on the light ranging and detecting (LIDAR) method, and photoluminescence. Table 2 summarizes the LODs of several explosive-related compounds (ERC) and EM obtained by the techniques described in this section. 

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. 

Studies of art works both for pigment identification in paintings using LIBS and Raman microscopy [177] and for on-line optical diagnostics [178] have recently been reported. 

Figure 1-21. The principle of the novel miniaturised Raman/LIBS combined spectrometer for the...

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