Abstract
We have utilized the relative intensity of magnesium lines originated from the Mg I at 285.2 nm and Mg II at 280.27, 279.55 nm to measure the plasma electron temperature. The plasma was produced via interaction of Nd:YAG laser with solid aluminum target contains traces of magnesium. The magnesium lines were found to suffer from optical thickness which manifests itself on the form of scattered points around the Saha-Boltzmann line. We have utilized a simple method used for rapid calculation to the amount of absorption to these lines via comparison of the electron densities as deduced from magnesium lines to that evaluated from the optically thin hydrogen Hα line at 656.27 nm appeared in the same spectra under the same condition. A correction to the magnesium spectral lines intensities was carried out; hence the corrected temperatures were re-evaluated. The measurements were repeated at different delay times ranging from 1 to 5 μsec. This work emphasizes on the importance of correcting the emitted spectral line intensity against the effect of self absorption before using them in the calculation of plasma electron temperature in laser induced breakdown spectroscopy (LIBS) experiments.
Highlights
The laser induced breakdown spectroscopy (LIBS) technique is one of the potentially growing applied techniques used in the field of elemental analysis, because of its simplicity and non-contact nature [1,2,3,4,5,6,7,8,9,10]
This work emphasizes on the importance of correcting the emitted spectral line intensity against the effect of self absorption before using them in the calculation of plasma electron temperature in laser induced breakdown spectroscopy (LIBS) experiments
A Voigt fitting and the extraction of the Lorentzian full width at half maximum (FWHM) from the Mg II ionic lines at wavelengths of 280.27, 279.55 nm and the Mg I line at 285.2 nm as well as to that of the Hα-line was carefully done using home made software running in MATLAB package
Summary
The LIBS technique is one of the potentially growing applied techniques used in the field of elemental analysis, because of its simplicity and non-contact nature [1,2,3,4,5,6,7,8,9,10]. The measurement of the electron density through Stark broadening effect requires a line which is free from self absorption [12,13]. The formation of the plasma in air shows, in general, a strong gradient of temperature due to the cooling effect of the surrounding air [14] These cold peripheries of the plasma contain a high concentration of the atoms at the low laying atomic states which can cause a strong re-absorption to the emitted radiation lines [1517]. The Mg II ionic lines are a good example of this effect because they are either a resonance lines like; the h and k lines at 279.55 and 280.27 nm respectively, or they are relatively intense These lines would be good candidates for calculating the plasma electron temperature. On the other hand the appearance of the Mg I-resonance line at 285.2 nm provides a assurance chance to construct the Saha-Boltzmann plot with the help of the Mg II lines, but this line is a resonance line, one should expect that it may be subjected to the effect of self absorption
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
