This paper presents time-resolved and space-integrated laser-induced breakdown spectroscopic (LIBS) analysis of copper and brass plasma. It was observed that copper emission is very strong during the first hundred nanoseconds of the plasma, but then some lines (e.g., at 327.4？nm) decrease in intensity, while others (e.g., 521.8？nm) slightly increase. Zinc lines, on the other hand, did not decrease significantly in intensity even two microseconds after ablation, but they became narrower due to the decrease of the density of free electrons. Copper line intensities showed the same characteristics regardless whether the plasma was created in a metallic copper or brass sample. Assuming local thermodynamic equilibrium, plasma temperature, and electron density is obtained from Boltzmann plot and Lorentzian profile fitting, respectively. The effect of subsequent irradiation on the same spot was investigated, and the number of necessary shots for surface cleaning was determined. 1. Introduction Laser-induced breakdown spectroscopy (LIBS) has reached an advanced level of development as a technique for elemental analysis and plasma diagnostics, with several published books and review papers covering many aspects of its nature and applications [1–6]. The great potential of LIBS lays in the simplicity of its setup: a pulsed laser beam with sufficient energy (usually several tens of mJ) is focused onto a target surface so that to cause its ablation, leading to rapid generation of an expanding plasma. Plasma contains excited atoms, ions, and molecules that emit light with characteristic wavelengths upon relaxation. Collection and analysis of the plasma light reveals the constituent elements of the interrogated surface, as well as their state (ionization level, temperature, and electron density). Despite numerous studies on LIBS, there remain quite a few challenges for the development of a turn-key LIBS system, which require some laboratory work. In particular, LIBS signal depends critically on the properties of the plasma, such as temperature and electron density, and these, in turn, vary significantly on a great range of values of laser parameters (beam energy, duration, wavelength, focusing), physical and chemical properties of the sample (composition, material matrix), the ambient in which the plasma is expanding (gas composition, state of flow, pressure), the signal acquisition systems (ICCD versus CCD cameras, acquisition time delay and acquisition time window), just to name a few. Hence, a full description of LIBS signal requires a full command or knowledge of
References
[1]
D. A. Cremers and L. J. Radziemski, Handbook of Laser-Induced Breakdown Spectroscopy, John Wiley & Sons, Chichester, UK, 2006.
[2]
A. W. Miziolek, V. Palleschi, and I. Schechter, Eds., Laser-Induced Breakdown Spectroscopy, Cambridge University Press, Cambridge, UK, 2006.
[3]
J. P. Singh and S. N. Thakur, Eds., Laser-Induced Breakdown Spectroscopy, Elsevier Science, Amsterdam, The Netherlands, 2007.
[4]
C. Pasquini, J. Cortez, L. M. C. Silva, and F. B. Gonzaga, “Laser induced breakdown spectroscopy,” Journal of the Brazilian Chemical Society, vol. 18, no. 3, pp. 463–512, 2007.
[5]
C. Aragón and J. A. Aguilera, “Characterization of laser induced plasmas by optical emission spectroscopy: a review of experiments and methods,” Spectrochimica Acta B, vol. 63, no. 9, pp. 893–916, 2008.
[6]
D. W. Hahn and N. Omenetto, “Laser-induced breakdown spectroscopy (LIBS), part I: review of basic diagnostics and plasmaparticle interactions: still-challenging issues within the analytical plasma community,” Applied Spectroscopy, vol. 64, no. 12, pp. 335A–366A, 2010.
[7]
I. Rauschenbach, E. K. Jessberger, S. G. Pavlov, and H. W. Hübers, “Miniaturized laser-induced breakdown spectroscopy for the in-situ analysis of the martian surface: calibration and quantification,” Spectrochimica Acta B, vol. 65, no. 8, pp. 758–768, 2010.
[8]
N. L. Lanza, R. C. Wiens, S. M. Clegg et al., “Calibrating the ChemCam laser-induced breakdown spectroscopy instrument for carbonate minerals on Mars,” Applied Optics, vol. 49, no. 13, pp. C211–C217, 2010.
[9]
R. E. Russo, X. L. Mao, C. Liu, and J. Gonzalez, “Laser assisted plasma spectrochemistry: laser ablation,” Journal of Analytical Atomic Spectrometry, vol. 19, no. 9, pp. 1084–1089, 2004.
[10]
L. Fornarini, V. Spizzichino, F. Colao, R. Fantoni, and V. Lazic, “Influence of laser wavelength on LIBS diagnostics applied to the analysis of ancient bronzes,” Analytical and Bioanalytical Chemistry, vol. 385, no. 2, pp. 272–280, 2006.
[11]
N. M. Shaikh, S. Hafeez, and M. A. Baig, “Comparison of zinc and cadmium plasma parameters produced by laser-ablation,” Spectrochimica Acta B, vol. 62, no. 12, pp. 1311–1320, 2007.
[12]
R. Qindeel, M. S. Dimitrijevic, N. M. Shaikh, N. Bidin, and Y. M. Daud, “Spectroscopic estimation of electron temperature and density of zinc plasma open air induced by Nd: YAG laser,” The European Physical Journal Applied Physics, vol. 50, no. 3, Article ID 30701, pp. 1–7, 2010.
[13]
G. Cristoforetti, S. Legnaioli, V. Palleschi, A. Salvetti, and E. Tognoni, “Influence of ambient gas pressure on laser-induced breakdown spectroscopy technique in the parallel double-pulse configuration,” Spectrochimica Acta B, vol. 59, no. 12, pp. 1907–1917, 2004.
[14]
G. W. Rieger, M. Taschuk, Y. Y. Tsui, and R. Fedosejevs, “Comparative study of laser-induced plasma emission from microjoule picosecond and nanosecond KrF-laser pulses,” Spectrochimica Acta B, vol. 58, no. 3, pp. 497–510, 2003.
[15]
B. Le Drogoff, M. Chaker, J. Margot et al., “Influence of the laser pulse duration on spectrochemical analysis of solids by laser-induced plasma spectroscopy,” Applied Spectroscopy, vol. 58, no. 1, pp. 122–129, 2004.
[16]
V. K. Unnikrishnan, K. Alti, R. Nayak et al., “Optimized LIBS setup with echelle spectrograph-ICCD system for multi-elemental analysis,” Journal of Instrumentation, vol. 5, no. 4, Article ID P04005, pp. 1–16, 2010.
[17]
X. L. Mao, A. C. Ciocan, and R. E. Russo, “Preferential vaporization during laser ablation inductively coupled plasma atomic emission spectroscopy,” Applied Spectroscopy, vol. 52, no. 7, pp. 913–918, 1998.
[18]
M. Gagean and J. M. Mermet, “Study of laser ablation of brass materials using inductively coupled plasma atomic emission spectrometric detection,” Spectrochimica Acta B, vol. 53, no. 4, pp. 581–591, 1998.
[19]
O. V. Borisov, X. L. Mao, A. Fernandez, M. Caetano, and R. E. Russo, “Inductively coupled plasma mass spectrometric study of non-linear calibration behavior during laser ablation of binary Cu–Zn alloys,” Spectrochimica Acta B, vol. 54, no. 9, pp. 1351–1365, 1999.
[20]
V. Margetic, A. Pakulev, A. Stockhaus, M. Bolshov, K. Niemax, and R. Hergenr？der, “Comparison of nanosecond and femtosecond laser-induced plasma spectroscopy of brass samples,” Spectrochimica Acta B, vol. 55, no. 11, pp. 1771–1785, 2000.
[21]
V. Margetic, K. Niemax, and R. Hergenr？der, “A study of non-linear calibration graphs for brass with femtosecond laser-induced breakdown spectroscopy,” Spectrochimica Acta B, vol. 56, no. 6, pp. 1003–1010, 2001.
[22]
C. Liu, X. L. Mao, S. S. Mao, X. Zeng, R. Greif, and R. E. Russo, “Nanosecond and femtosecond laser ablation of brass: particulate and ICPMS measurements,” Analytical Chemistry, vol. 76, no. 2, pp. 379–383, 2004.
[23]
A. B. Gojani and J. J. Yoh, “New ablation experiment aimed at metal expulsion at the hydrodynamic regime,” Applied Surface Science, vol. 255, no. 22, pp. 9268–9272, 2009.
[24]
Y. Ralchenko, A. E. Kramida, J. Reader, and NIST ASD Team, “NIST Atomic Spectra Database (version 4.0),” http://physics.nist.gov/asd, 2012.
[25]
A. Thorne, U. Litzen, and S. Johanson, Spectrophysics: Principles and Applications, Springer, Berlin, Germany, 2nd edition, 1999.
[26]
L. J. Radziemski and D. A. Cremers, “Spectrochemical analysis using laser plasma excitation,” in Laser-Induced Plasmas and Applications, L. J. Radziemski and D. A. Cremers, Eds., chapter 7, p. 298, Marcel Dekker, New York, NY, USA, 1989.
[27]
B. Német and L. Kozma, “Time-resolved optical emission spectrometry of Q-switched Nd: YAG laser-induced plasmas from copper targets in air at atmospheric pressure,” Spectrochimica Acta B, vol. 50, no. 14, pp. 1869–1888, 1995.
[28]
M. S. Dimitrijevi？ and S. Sahal-Bréchot, “Stark broadening of neutral zinc spectral lines,” Astronomy and Astrophysics Supplement Series, vol. 140, no. 2, pp. 193–196, 1999.
