Investigation on the role of air in the dynamical evolution and thermodynamic state of a laser-induced aluminium plasma by spatial- and time-resolved spectroscopy
Authors: Cristoforetti G., Lorenzetti G., Legnaioli S., Palleschi V.
Autors Affiliation: National Institute of Optics, Research Area of National Research Council, Via G.Moruzzi, 1 – 56124 Pisa, Italy;
Institute of Chemistry of Organometallic Compounds, Research Area of National Research Council, Via G.Moruzzi, 1 – 56124 Pisa, Italy
Abstract: The amount and the spatial distribution of air atoms and ions in a laser-induced plasma in ambient air provide important information about the formation of the plasma and its successive evolution history. For this reason, in the present work, the air mixing in a laser-induced plasma in air at atmospheric pressure and its influence on its thermodynamic evolution were studied. Information about spatial distributions of atoms and ions from Al, N and O were achieved by Abel-inverted spectra in the plume. The occurrence of LTE in the plume was also assessed by the utilization of theoretical criteria, and by the analysis of experimental spectra. Aluminium atoms and ions were found to be in LTE, while nitrogen and oxygen were not because of their longer times of relaxation toward equilibrium. Nitrogen was found to be over-ionized with respect to Saha-Eggert equilibrium, indicating that the plasma is recombining. Experimental observations suggest that the concentration of air species in the plasma is larger than that of aluminium, even in the region closer to the target, where the aluminium lines are stronger. In the front part of the plume only emission lines from air species were observed. The results suggest that a Laser-Supported Detonation (LSD) regime occurs during the trailing part of the laser pulse, resulting in the strong inclusion into the plasma of air elements. In this scenario, also the thermodynamic history of the plume is affected by the predominance of air species. (C) 2010 Elsevier B.V. All rights reserved.
Journal/Review: SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY
Volume: 65 (9/10) Pages from: 787 to: 796
KeyWords: Local thermodynamic equilibrium; laser-induced plasma; spatial-resolved spectroscopy; Abel inversion; Ambient air effectsDOI: 10.1016/j.sab.2010.07.002Citations: 41data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2019-10-13References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here