| The laser-induced breakdown spectroscopy (LIBS) technique has been developed as a useful method for determining the elemental composition of different materials either in solid, liquid or gaseous phase. The use of LIBS as an analytical tool has been considerably grown in the recent ten years. At present, pulsed laser induced plasma technique is a powerful and available method, and has been widely used in many important fields such as material process, superconductor thin film preparation, nano-technique and trace element analysis. LIBS can be regarded as a universal sampling, atomization excitation and ionization source, since laser-induced plasmas can be produced in gases ionization source. Since laser-induced plasmas can be produced in gases or liquids, as well as from conducting or non-conducting solid samples.Although many experimental and theoretical researches have been carried out on the laser produced plasma dynamics, the time and spatial-resolved spectral properties in recent years, it is still an unsolved problem. Because the forming of laser produced plasma is a very complicated process not only related to the properties of the laser and buffer gas but also the physical-chemical properties of the solid sample. The study on the emission spectral from the laser induced plasma provides a most effective method to explore the dynamics of the laser induce plasma. In this paper, some experimental investigations were carried out with the samples of metal Al and have been calculated the plasma temperature and the electron density. In addition, spectrochemical analysis using LIBS has been proven to be extremely versatile. This technique for solid sample analysis has been successfully applied to the on-line industry.In this paper, we first discussed using laser-induced breakdown spectroscopy on a quantitative analysis of the atmospheric experiments.The oxygen content and nitrogen content in air were detected on the assumption that there were only oxygen and nitrogen constituents in the air. The results coincide well with the fact. Then, we have measured the Al plasma emission spectroscopy and Al plama time-resolved spectroscopy in the range of 340～400nm and calculated the electron temperature and electron by STARK broadening of the emission spectral line respectively.Experimental results show that the experimental conditions meet local thermal equilibrium assumptions.This paper consists of six chapters .The main contents are listed as following:This paper contains four parts. The first part is the chapter one of my dissertation. Its main content is expatiating on the technique characters,development,actuality and using in solid,liquid state,gaseity of LIBS.The second part consists of chapter 2 and chapter 3. In chapter 2, the mechanism and character of laser plasma were introduced in detail. And the experimental apparatus involved in the investigation is consisted of three principal systems, viz. laser sources, spectrum detection system and data acquisition system. A detail description of these systems was given in Chapter 3. It is including two sides:(1)established the gaseity LIBS experimental system. It can be analyzed the LIBS spectral observation and data about the air(.2)established the solid LIBS experimental system. It can be analysised the LIBS spectral observation and data about Al.The third part consists of chapter 4 and chapter 5. In chapter 4 we discussed using laser-induced breakdown spectroscopy on a quantitative analysis of the atmospheric experiments. In order to investigate the feasibility of quantitative analysis with laser-induced breakdown spectroscopy, plasmas were produced by a Q-switched Nd:YAG laser interacted with the air at atmospheric pressure, then the light of plasmas entered the monochrometer and transferred into an electric signal, and the spectra of these plasmas in the range of 390～850nm were stored and analyzed by the calibration-free model under the condition of delay time of 3μs and gating pulse of 0. 4μs,the temperature of plasmas, which was in local thermal equilibrium(LTE),was 1. 2×105kwhich was obtained by means of the two-dimensional Boltzmann plane. The 23.2% oxygen content and 75.4% nitrogen content in air were detected on the assumption that there were only oxygen and nitrogen constituents in the air. The results coincide well with the fact.Chapter 5 we focused on the Al metal plasma characteristics. In Al metal lab, laser pulse energy was fixed at 70 mJ, and laser interacted with the air at atmospheric pressure. In order to investigate the feasibility of quantitative analysis with Al (Length: 40 mm and width of 10 mm, thickness of 1 mm, and the purity of 99.9%)laser-induced breakdown spectroscopy, plasmas were produced by a Q-switched Nd:YAG laser interacted with the air at atmospheric pressure, then the light of plasmas entered the monochrometer and transferred into an electric signal, and the spectra of these plasmas in the range of 340～400nm were stored and analyzed by the calibration-free model under the condition of delay time of 3μs and gating pulse of 0. 4μs,the temperature of plasmas, which was in local thermal equilibrium(LTE),was 8060k which was obtained by means of the two-dimensional Boltzmann plane. Using Lorenz fitting, we obtained the largest half-width lines. According to the formulaΔλ1 2=2ω1N01e6, we calculated the electron density . In this experimental condition, the electron density is 3. 334×1016cm ?3. Experimental results show that the experimental conditions meet local thermal equilibrium assumptions. It built a strong basis for the further study and experiment of other solid metal plasma.In the last chapter, the summation and the conclusion of this work and some expectation of the future work are presented. In the future ,experimental investigations were carried out with the samples of liquid solutions, in the attempt of establishing a LIBS based technique for ocean environmental detection. We may be also through the use of femtosecond laser to research. On the analysis of time-resolved spectroscopy of plasma induced by femtosecond laser, we could have a further understanding of the kinetics process on some particles during the course of evolution in laser-induced plasmas, as well as of the reaction kinetics in which various kinds of particles and the ambient gas interact to produce new particles. According to the analysis, the micro-mechanism of laser ablation materials could be explained further. It is of great significance to the process of laser micro machining, optimizing the experimental condition of laser ion beam sputtering technology and improving the quality of films. |
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