Evaluation of self-absorption of manganese emission lines in Laser Induced Breakdown Spectroscopy measurements

Year: 2006

Authors: Bredice F., Borges F.O., Sobral H., Villagran-Muniz M., Di Rocco H.O., Cristoforetti G., Legnaioli S., Palleschi V., Pardini L., Salvetti A., Tognoni E.

Autors Affiliation: Centro de Investigaciones Opticas, P.O. Box 124, (1900) La Plata, Argentina;
Instituto de Física, Universidade Federal Fluminense, UFF, Campus da Praia Vermelha-Gragoatá, 24210-340 Niterói, Rio de Janeiro, Brazil;
Laboratorio de Fotofísica, Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Apartado Postal 70-186 México Distrito Federal, P. O. Box 04510, Mexico;
Instituto de Física “Arroyo Seco”, Facultad de Ciencias Exactas, U.N.C.P.B.A., Pinto 399, 7000 Tandil, Argentina;
Applied Laser Spectroscopy Laboratory, IPCF-CNR, Area della Ricerca di Pisa, Via G. Moruzzi 1, 56124 Pisa, Italy

Abstract: This paper is part of a more general study aimed to the determination of the best experimental procedures for reliable quantitative measurements of Fe-Mn alloys by LIBS. In this work, attention is pointed on the self-absorption processes, whose effect deeply influences the LIBS measurements, reflecting in non-linear calibration curves. The effect of self-absorption on the line intensity can be quantified by defining a self-absorption coefficient, that measures the deviation of the line intensity from the linear extrapolation of the curve of growth in the optically thin regime. The authors demonstrated in a previous paper that self-absorption coefficients could be calculated once the electron density of the plasma is known and the Stark coefficients of the lines are available. However, when the Stark coefficients of the lines of interest are not known, a different approach is needed. In this work a new method for evaluation of self-absorption coefficients in LIBS measurements is presented, which does not require the knowledge of Stark coefficients. In order to understand the basic principles and setting out the theoretical tools that will be used for the analysis of the alloys, a preliminary study was done on pure Mn; LIBS spectra were acquired in different experimental conditions, at different laser energies and different delays after the laser irradiation of the sample. Moreover, collinear double pulse measurements were also performed. Analytical relations were derived and experimental procedures devised for evaluation of the self-absorption coefficients of several Mn lines, which are important for characterization and control of the experimental conditions in which the analysis is performed. (c) 2006 Elsevier B.V. All rights reserved.


Volume: 61 (2)      Pages from: 1294  to: 1303

KeyWords: Fe-Mn alloys; Laser-Induced Breakdown Spectroscopy; Self-absorption
DOI: 10.1016/j.sab.2006.10.015

Citations: 116
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