%0 Journal Article
%T Experimental Study of Laser-Induced Brass and Copper Plasma for Spectroscopic Applications
%A Ardian B. Gojani
%J ISRN Spectroscopy
%D 2012
%R 10.5402/2012/868561
%X 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¨C6]. 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
%U http://www.hindawi.com/journals/isrn.spectroscopy/2012/868561/