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Material analysis via laser-induced breakdown spectroscopy

Contact : Jörg Hermann

Laser-induced breakdown spectroscopy (LIBS) is an emerging analytical technique that takes advantage from the combination of several features : LIBS enables rapid measurements in ambient air without any requirement of sample preparation. The contactless and almost non-destructive measurements are promising for many applications, such as in-situ control of industrial processes, quality control, and environmental survey. However, the accuracy of LIBS measurements is mostly qualitative or semi-quantitative for many materials. The low precision is related to the difficulties of calibrating the measurements. Due to strong matrix effects, LIBS analyses have to be calibrated with standard samples of compositions close to the sample to be analyzed. To overcome these difficulties, so-called calibration-free LIBS measurement procedures have been developed. Based on modeling of the plasma emission, the composition is deduced from the best agreement between calculated and measured spectra.

In the LP3 laboratory, we develop a calibration-free LIBS measurement procedure based on the calculation of the spectral radiance of a plasma in local thermodynamic equilibrium. The method was patented by the CNRS (US8942927 B2). It accounts for self-absorption of spectral lines and considers temperature and density gradients within the plasma. By the characterization of the plasma and it’s expansion dynamics, our investigations aim to improve our understanding of the mechanisms involved into the processes of laser ablation, plasma formation and plume expansion. On one hand, we search for appropriate experimental conditions that enable simple and accurate modeling of the plasma emission spectrum. On the other hand, the improved knowledge of the laser plasma allows us to improve the model and to enable quantitative LIBS measurements of all kind of materials. In particular, organic materials present extra difficulties due to the strong reactivity of the involved plasma species. The chemical processes within the laser-produced plasma and their modeling are therefore of particular interest.

Fig. 8. Emission spectrum of a plasma produced by laser ablation of aluminum. Comparison to the spectral radiance of a nonuniform plasma in local thermodynamic equilibrium. La simulation shows that atomic lines are emitted mainly from the hot plasma core whereas molecular bands originate from the cold peripheral volume.

Fig. 9. Elemental composition of alumina aerosols deduced from the LIBS analyses of spectra recorded for different delays between detector gate and laser pulse. The reference composition (black color) corresponds to stoichiometric Al2O3. Accurate measurements are possible for short delays exclusively. The low precision for large delays is attributed to the deviation from local thermodynamic equilibrium.

Publications :

Gerhard C., Tasche D., Uteza O., Hermann J., Investigation of nonuniform surface properties of classically-manufactured fused silica windows, Appl. Opt. 56, 7427-7434 (2017)

Gerhard C., Hermann J., Sarnet T., Nardini J.-M., Viöl W., Detection of Lead and Arsenic Soil Pollution in Abandoned Industrial Poles to the South of Marseille, France by Laser-Induced Breakdown Spectroscopy, Scottish Journal of Arts, Social Sciences and Scientific Studies 26, 95-110 (2015)

Gerhard C., Hermann J., Mercadier L., Loewenthal L., Axente E., Luculescu C.R., Sarnet T., Sentis M., Viöl W., Quantitative analyses of glass via laser-induced breakdown spectroscopy in argon, Spectrochim. Acta Part B 101, 32–45 (2014)

Axente E., Hermann J., Socol G., Mercadier L., Beldjilali S., Cirisan M., Luculescu C.R., Ristoscu C., Mihailescu I.N., Craciun V., Accurate analysis of indium-zinc oxide thin films via laser-induced breakdown spectroscopy based on plasma modeling, J. Anal. At. Spectrom. 29, 553-564 (2014)

Axente E., Socol G., Beldjilali S.A., Mercadier L., Luculescu C.R., Trinca L.M., Galca A.C., Pantelica D., Ionescu P., Becherescu N., Hermann J., Craciun V., Quantitative analysis of amorphous indium zinc oxide thin films synthesized by Combinatorial Pulsed Laser Deposition, Appl. Phys. A 117, 229–236 (2014)

Yip W.L., Mothe E., Beldjilali S., Hermann J., Accumulation of Air in Polymeric Materials Investigated by Laser-Induced Breakdown Spectroscopy, J. Appl. Phys. 111, 063108 1-6 (2012)

Popescu A.C., Beldjilali S., Socol G., Craciun V., Mihailescu I.N., Hermann J., Analysis of indium zinc oxide thin films by laser-induced breakdown spectroscopy, J. Appl. Phys. 110, 083116 1-8 (2011)

Mercadier L., Hermann J., Grisolia C., Semerok A., In-depth analysis of ITER-like samples composition using laser-induced breakdown, J. Nucl. Mater., 414, 485-491 (2011)

Mercadier L., Grisolia C., Roche H. Semerok A., Hermann J., Pocheau C., Thro P.Y., Sirven J.B., Weulersse J.M., Mauchien P., Sentis M., In-situ tritium measurements and control by laser techniques, Fusion Sci. Technol. 60, 1049-1052 (2011).

Beldjilali S., Borivent D., Mercadier L., Mothe E., Clair G., Hermann J., Evaluation of minor element concentrations in potatoes using laser-induced breakdown spectroscopy, Spectrochim. Acta Part B 65, 727-733 (2010)