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Title: Optical Emission Studies of Laser Induced Silicon Germanium, Tin and Lead Plasma
Authors: Iqbal, Javed
Keywords: Laser Spectroscopy / Atomic Physics
Issue Date: 2018
Publisher: University of Azad Jammu and Kashmir Muzaffarabad, Pakistan
Abstract: Laser induced breakdown spectroscopy (LIBS) is a technique which provides qualitative and quantitative information from the emission spectra of the laser produced plasma of the metallic materials in various environments. In the present work, we have studied the optical emission spectra of the laser produced silicon (Si), Germanium (Ge), Tin (Sn) and Lead (Pb) plasma and also deduced the plasma parameters and atomic parameters by this technique. We have used the fundamental 1064 nm and second harmonic 532 nm of a Q-switched pulsed Nd:YAG laser (Quantel, Brilliant-B, France) for ablation and generating the plasma. The emission spectra of the laser produced plasma were captured using a set of four spectrometers (Ocean Optics), each spectrometer was equipped with 5 micron slit width and covering the spectral region between 200 – 720 nm. In somaqe experiments, we also used another set of four spectrometers (Avantes, Holland), each spectrometer was equipped with 10 micron slit width and covering the spectral region between 250 – 875 nm. The experimentally observed line profiles of the several neutral and ionic species have been used to extract the line widths, plasma or excitation temperatures, electron number densities and atomic parameters such as branching fractions, transition probabilities and relative line strength. The Plasma temperatures were determined using four different techniques; two line ratio method, Boltzmann plot, Saha-Boltzmann plot and Marotta's technique whereas electron densities were deduced from the Stark broadened line profiles as well as from the Boltzmann-Saha relation. From the observed line intensities of the spatially registered spectra of silicon, we have determined the plasma temperature in the range of 8500 K to 9500 K and electron density in the range of 1x1017 cm-3 to 4 x1017 cm-3 at different laser energies. The plasma temperature for germanium (Ge) has been determined in the range (9000 – 11400 K) , (9500 – 10500 K) , for Tin (Sn) and (9000 - 10500 K) for Lead (Pb) and the electron densities have been deduced in the range (0.5 – 5.0)×1017cm-3 for Ge, (0.5 – 5.0)×1017cm-3 for Tin and (3.5 – 6.5)×1016cm-3 for lead depending on the laser pulse energy to produce the plasma. The Full width at half maximum (FWHM) of a number of neutral and singly ionized silicon, germanium, tin and lead lines have been extracted by the Lorentzian fit to the experimentally observed line profiles. We have compared the experimentally measured relative line strengths for the 4p5s 3P0,1,2 → 4p2 3P0,1,2 multiplet with that of calculated in the LS-coupling scheme revealing that the intermediate coupling scheme is more appropriate for the level designations in germanium. In addition, the LIBS, technique has also been exploited to experimentally determine the branching fractions and transition probabilities for fourteen spectral lines originating from the 3p4s→3p2 transition array of silicon (Si I), fifteen lines of the 5p5d→5p2 transition array in tin and eleven lines of the 6p7s → 6p2 transition array in lead, whereas the absolute values of the transition probabilities have been calculated by combining the experimental branching fractions with the life times of the excited levels. Our new results are comparable to that reported in the literature, where available.
Gov't Doc #: 19461
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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