A Procedure for Estimating the Electron Temperatureand the Departure of the LTE Condition in a Time-Dependent, Spatially Homogeneous, Optically Thin Plasma |
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Authors: | F Bredice F O Borges H O Di Rocco R S Mercado M Villagrán-Muniz V Palleschi |
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Institution: | 1. Centro de Investigaciones Opticas, P.O. Box 124 C. P.1900, La Plata, Argentina 2. Laboratório de Plasma e Espectroscopia At?mica, Instituto de Física, Universidade Federal Fluminense, 24210-340, Niterói, Rio de Janeiro, Brazil 3. Instituto de Física Arroyo Seco (IFAS), Universidad Nacional del Centro, Pinto 399, Tandil, Argentina 4. Grupo de Espectroscopia óptica de Emisión y Láser (GEOEL), Universidad del Atlántico, A.A. 1890, Barranquilla, Colombia 5. Laboratorio de Fotofísica, Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Apartado Postal 70-186, México, 04510, Mexico 6. Applied Laser Spectroscopy Laboratory, ICCOM-CNR, Area della Ricerca di Pisa, Via G. Moruzzi 1, 56124, Pisa, Italy
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Abstract: | We present a method to estimate the temperature of transient plasmas and their degree of departure from local thermodynamic equilibrium conditions. Our method is based on application of the Saha–Boltzmann equations on the temporal variation of the intensity of the spectral lines of the plasma, under the assumption that the plasmas at the different times when the spectra were obtained are in local thermodynamic equilibrium. The method requires no knowledge of the spectral efficiency of the spectrometer/detector, transition probabilities of the considered lines, or degeneracies of the upper and lower levels. Provided that the conditions of optically thin, homogeneous plasma in local thermodynamic equilibrium are satisfied, the accuracy of the procedure is limited only by the precision with which the line intensities and densities can be determined at two different temperatures. The procedure generates an equation describing the temporal evolution of the electron number density of transient plasmas under local thermodynamic equilibrium conditions. The method is applied to the analysis of two laser-induced breakdown spectra of cadmium at different temperatures. |
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