الفهرس 
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Abstract
In the present work a detailed study has been performed on the effect of laser parameters on the plasma emission and plasma parameters of laser induced breakdown spectroscopy (LIBS) technique. The work starts by studying the influence of the laser pulse duration (nanosecond (ns) and femtosecond (fs)) at A.=248 nm on the laser-induced plasma parameters and the quantitative analysis results for elements such as Sn, Zn and Pb, in different types of bronze alloys adopting LIBS in ambient atmosphere. Binary (Sn-Cu), ternary (Sn-Zn-Cu or Sn-Pb-Cu) and quaternary (Sn-Zn- Pb-Cu) reference alloys characterized by chemical composition and metallurgical features similar to those used in Roman times, were employed throughout the study. Calibration curves, featuring linear regression coefficients over 98٪, were obtained for tin, lead and zinc; the minor elements in the bronze alloys (using the internal standardization method) .The effects of laser pulse duration and energy on laser-induced plasma parameters, namely the excitation temperature and the electron density have been studied to optimize the analysis. To confirm the obtained calibration curves a certified quaternary bronze sample has been measured and comparison has been held between the LIBS measured values (for Sn, Pb and Zn) with both pulse durations (ns and fs) and the standard values .A very good agreement between measured and real values has been obtained for both nano and femtosecond lasers. LIBS analysis was carried on three real metal objects and the spectra obtained have been used to estimate the type and elemental composition of the alloys based on the calibration curves produced with the reference alloys. In the second part of this work, experimental results have been compared to theoretical data obtained via mode ling of the laser ablation process with the aim to optimize quantitative analysis in ambient atmosphere. Calibration curves were plotted from the measured data in both cases and compared with the theoretical values obtained from the model. The slopes showed a very good agreement between the theoretical and experimental data for each element (Sn, Zn and Pb), indicating that the evaporation process considered in the model is the main process involved in LIBS analysis at the selected experimental conditions. Plasma temperature temporal behavior was deduced using Boltzmann plots, while the electron density has been determined from the Stark broadening of spectral lines. Plasma emission continuum spectrum was found to decrease much more rapidly with the delay time for femtosecond laser plasma excitation with respect to the nanosecond one. This behavior significantly reduces the continuum emission in the measurement window. The potential of LIBS technique for accurate quantitative analysis could be greatly improved using experimental setup based on the use of two laser pulses suitably retarded. The third part of this work dealt with double pulse LIBS is performed on a set of certified bronze samples, reference calibration curves were built and Limits Of Detection (LOD) were calculated in order to obtain quantitative information about the composition of three ancient bronze coins. The coins are Punic, of a kind struck in many Punic mints of the Mediterranean basin. The detection limits for the elements of interest were calculated under the optimum conditions for the double-pulse configuration and compared with those obtained under the optimum conditions for single-pulse configuration. Significantly improved detection limits were achieved, for all the elements investigated in case of double pulse. The results obtained in this thesis are very useful in the future use of portable or mobile LIBS systems for in situ qualitative and quantitative elemental analysis of bronze artifacts in museums and archaeological sites.