الفهرس 
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Abstract
Laser Induced Breakdown Spectroscopy (LIBS) or Laser Induced Plasma Spectroscopy (LIPS) was intensively studied in the last decade as a new analytical technique. This technique deals with the study of the spectral distribution of line intensities and the line shapes, of the optical emission and allow for an acceptable spatial & temporal resolution of the detected spectra. It is increasingly seen as a viable analytical technique. It is a promising tool for the analysis of trace impurities in metals. In LIBS technique, a powerful laser pulse is focused on a surface, a tiny amount of material is vaporized and through further photon absorption, it is heated up until it ionize and expand from the sample surface as a plasma cloud. This laser induced plasma is a micro–source of light that can be analyzed spectrally and temporally resolved detection of characteristic emission by a spectrometer. The ability to determine the composition of a heavy metals in water surface is a milestone and has several applications. In this thesis, LIBS has been utilized to determine the elemental composition of heavy metals in sea water samples by forming micro plasma on the surface of four samples taken from lake Timsah – Ismailia City, Egypt . Two different Nd:YAG laser sources working at 1064-nm are synchronized for water surface measurements by a two-channel pulse generator and steered along the same path by using beam splitter (40/60 % at 1064nm) then focused into the surface of sea water samples. A lens was used to focus the beams on surface of the water. The detection system consists of a PI-Echelle spectrometer and ICCD camera.The plasma emission spectrum was recorded at several conditions for plasma therefore temporally resolved optical emission spectroscopy is used to investigate the evolution of plasma and spectral line intensity and to estimate plasma parameter such as electron density and plasma temperature as well as the limit of detection using different software such as Winspec, Gram 32.0 and ORIGIN PRO 8 software. The effect of gate time delay as well as inter-pulse delay has been studied by monitoring the behavior of the spectra lines. For surface water measurements the gate time delay varied from 500 nsec to 5000 nsec while, inter-pulse delay varied from 1 to 5 μsec and gate width in the range of 1000 nsec, 5000 nsec and 10000 nsec were observed. Optimum experimental results for the double pulse LIBS under water measurements are 1000 nsec and 1500 nsec gate time delays, 1 μsec to 3 μsec inter-pulse delay and 10000 nsec gate width. The plasma excitation temperature was determined using Boltzmannplot method of Hydrogen and Nitrogen lines observed from the collected samples. the temperature calculated for the plasma varied from 3952 °K to 13453 °K . The electron density was derived from the line shape data of the stark broadened Hα (656.29 nm). The obtained electron density varied from Ne=(4× 1017- 6.0 × 1017 cm3). For quantitative analysis purposes, calibration curves of Co SO4.7H2O and Cd(CH3CO2)2 have been prepared. The calibration curves were constructed to estimate the limit of detection (LOD in µg/liter). The minimum calculated values for LODs in water 17.4 µg/liter and 19.161 µg/liter for Cadmium and Cobalt respectively.