Spatial distributions of the number densities of neutral atoms and ions for the different elements in a laser induced plasma generated with a Ni-Fe-Al alloy |
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Authors: | C Aragón F Peñalba J A Aguilera |
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Institution: | (1) Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadía, 31006 Pamplona, Spain;(2) Fundación Inasmet, Paseo Mikeletegi, 2, 20009 San Sebastián, Spain |
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Abstract: | Spatially-resolved emission spectroscopy, including spatial devonvolution of the spectra, has been used to determine the three-dimensional
distributions of the relative number densities of neutral atoms and ions of the elements present in a laser-induced plasma
generated with a Ni-Fe-Al alloy. The method is based on the precise measurement of the local electronic temperature from Saha–Boltzmann
plots constructed with Fe I and Fe II lines. The plasma was generated in air at atmospheric pressure using a 1064-nm Nd:YAG
laser, and the emission was detected in the time window 3.0–3.5 μs. The ionization fraction was very high (above 0.9) for
the three elements in the sample, only decreasing behind the expanding plasma front. The relative number densities were obtained
from the emissivities of selected elemental lines as well as the temperature. The error in this procedure was estimated, and
it was found that it is largely due to the uncertainties in the transition probability values used. The spatial distributions
of the total relative number densities of the three elements were shown to coincide within the error, a result which is relevant
to the development of models of plasma emission used in analytical applications. The ratios of the total number densities
of the elements in the plasma were compared to their concentration ratios in the sample; however, the relatively high errors
in the relative number densities did not permit any definitive conclusions to be drawn about the stoichiometry of the laser
ablation process. |
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Keywords: | Laser-induced plasma spectroscopy LIBS Laser ablation Plasma characterization Number density |
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