الفهرس 
CHAPTER 1 : LASER INDUCED PLASMA SPECTROSCOPY- LIPSOnly 14 pages are availabe for public view
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Abstract
In this work first we have utilized some nanomaterial’s including zinc, silicon, aluminum, titanium and finally we have used the Nano silver nanoparticles. In each case, we have observed a strong enhanced emission from the plasma created from the pure nanomaterial. Then we have selected the silver nanoparticles of average size of 95±10 nm in this extensive study, which has been used as target to radiation from Nd: YAG laser at wavelengths of 355, 532 and 1064 nm in order to measure the laser induced-plasma spectroscopy (LIPS) from the Nano structured target in comparison to corresponding bulk silver under similar conditions. Echelle spectrograph in conjunction with fast ICCD camera was employed. In general, a strong emission was noticed from the Nano structured target with respect to bulk one which is known as plasma enhanced emission. The laser fluence was then detuned to the levels of plasma ignition threshold following the strong Ag I lines and was found amounted to 0.4±0.02, 0.34±0.04 and 0.27±0.035 J/cm2, while it is rather one order of magnitude larger from the corresponding bulk silver (4, 3.4 and 2.7 J/cm2) at the respective laser wavelengths of 355, 532 and 1064 nm. Modeling of the results based on the assumption of reduction of the thermal conduction length of the Nano particles to the limit of nanoparticle size was successfully applied to predict the measured values of thresholds. Strong enhanced emission from the Nano-based target is confirmed (Nano-Enhanced Laser Induced Breakdown Spectroscopy-NELIBS). Comments on other appeared Ag I spectral lines are also given. However, and in order to check the reliability of the assumed model , we have carried asset of subsidiary experiments to measure the first ionization potential of neutral atoms which should be determined at the thresholds of laser-induced optical breakdown. The induced plasmas at the surface of aluminum, silver, lead, indium and copper are created in laboratory air with focused, 5-ns pulsed Nd: YAG, 1064 nm IR radiation at fixed spot size of 2 ± 0.1 mm, the laser fluence is varied from 16 to 3 J/cm2. The first ionization potentials of Al I 396.2, Ag I 520.9, Pb I 405.8 and 406.2, In I 410.2 and Cu I 515.3 nm are measured to amount to 5.9 ± 0.2, 7.6 ± 0.3, 7.4 ± 0.2, 5.8 ± 0.1 and 7.7 ± 0.2 eV, respectively. The measured ionization energies for the different targets nicely agree with tabulated values, consequently, this agreement can be interpreted as confirmation for the laser-induced plasma threshold model and results given at the appendix. Finally, the resonance spectra of neutral silver indicate self-reversal in addition to self-absorption for the studied Ag I lines at the wavelengths of 327.9 nm and 338.2 nm. The center dip is associated with self-reversal due to self-absorption in the plasma. The Q-switched radiation of 355 nm, 532 nm, or 1064 nm from a Nd: YAG laser device generates the plasma at the surface of silver Nano-material targets, with experiments conducted in standard ambient temperature and pressure laboratory air. Procedures for recovery of the spectral line shapes confirm that over and above the effects of self-reversal, line shape distortion are important in the analysis. The work discusses parameters describing self-absorption when using fluence levels from 2 to 33 J/cm2 to generate the plasma. Furthermore, as a part of work, a calibration efforts that utilizes the hydrogen alpha line of the Balmer series at 656.27 nm show that the Ag I lines at 827.35 nm and 768.7 nm are optically thin and can be recommended as a suitable candidate to measure the plasma electron density. Moreover, we find a linear proportional bet camera delay time and enhancement factor In the attached appendix, we have studied the first ionization potential of neutral atoms is determined at the thresholds of laser-induced optical breakdown. The induced plasmas at the surface of aluminum, silver, lead, indium and copper are created in laboratory air with focused, 5- ns pulsed Nd: YAG, 1064 nm IR radiation. At fixed spot size of 2 ± 0.1 mm, the laser fluence is varied from 16 to 3 J/cm2. For several selected elements that show strong atomic emission lines, the first ionization potentials of Al I 396.2, Ag I 520.9, Pb I 405.8 and 406.2, In I 410.2 and Cu I 515.3 nm are measured to amount to 5.9 ± 0.2, 7.6 ± 0.3, 7.4 ± 0.2, 5.8 ± 0.1 and 7.7 ± 0.2 eV, respectively. The measured ionization energies for the different targets agree with tabulated values, consequently, this agreement can be interpreted as confirmation for the laser-induced plasma threshold.