No presente trabalho foi realizada uma análise de dois padrões de aço inoxidável ferrítico submetidos à ação de lasers pulsados, um no regime de nanosegundos e outro no regime de femtosegundos. Foram determinadas as temperaturas e densidades do plasma formado a partir da análise espectroscópica da radiação emitida em diferentes faixas espectrais, por diferentes espécies e em diferentes janelas de integração no tempo. As temperaturas foram obtidas de duas formas, pelo método do gráfico de Boltzmann e pela razão entre duas linhas. Os resultados foram comparados com o intuito de verificar se o método da razão conseguia recuperar os resultados obtidos pela abordagem do gráfico de Boltzmann. Foi observada uma grande concordância entre os dois métodos no regime de femtosegundos, ao passo que no regime de nanosegundos a recuperação das temperaturas não foi tão satisfatória. A densidade eletrônica do plasma foi determinada a partir do alargamento Stark e verificou-se que o plasma gerado pelo laser de nanosegundos era mais denso que aquele gerado no regime de femtosegundos. As densidades determinadas sob diferentes janelas de integração do sinal no tempo foram também comparadas sendo que aquelas relativas aos estágios iniciais do plasma eram maiores que aquelas de estágios finais. Com a obtenção das temperaturas e das densidades foi possível caracterizar totalmente o plasma e compará-lo com outros plasmas naturais e artificiais. / In this work, an analysis of two ferritic stainless steel standards irradiated by nanosecond and femtosecond pulsed lasers was carried out. The temperature and electronic density of the plasma were determined by spectroscopic analysis of the emission from different atomic species, in different spectral ranges and integration gates. The temperatures were evaluated by two methods: Atomic Boltzmann plot and two line ratio. The results were compared in order to verify if the two line ratio method can agree to the results evaluated by the Boltzmann plot method. An agreement between the two methods was observed in the femtosecond generated plasma, otherwise there was no sufficient agreement in the nanosecond generated plasma. The electronic density of the plasma was determined by Stark broadening and the nanosecond generated plasma is denser than the femtosecond generated one. The densities evaluated under different integration gates were compared and the earliest gates were denser than the final ones. The plasma temperature and density can completely characterize the plasma and a comparison between these ablation related plasma and a comparison between them and other natural and artificial plasmas was performed.

No presente trabalho foi realizada uma análise de dois padrões de aço inoxidável ferrítico submetidos à ação de lasers pulsados, um no regime de nanosegundos e outro no regime de femtosegundos. Foram determinadas as temperaturas e densidades do plasma formado a partir da análise espectroscópica da radiação emitida em diferentes faixas espectrais, por diferentes espécies e em diferentes janelas de integração no tempo. As temperaturas foram obtidas de duas formas, pelo método do gráfico de Boltzmann e pela razão entre duas linhas. Os resultados foram comparados com o intuito de verificar se o método da razão conseguia recuperar os resultados obtidos pela abordagem do gráfico de Boltzmann. Foi observada uma grande concordância entre os dois métodos no regime de femtosegundos, ao passo que no regime de nanosegundos a recuperação das temperaturas não foi tão satisfatória. A densidade eletrônica do plasma foi determinada a partir do alargamento Stark e verificou-se que o plasma gerado pelo laser de nanosegundos era mais denso que aquele gerado no regime de femtosegundos. As densidades determinadas sob diferentes janelas de integração do sinal no tempo foram também comparadas sendo que aquelas relativas aos estágios iniciais do plasma eram maiores que aquelas de estágios finais. Com a obtenção das temperaturas e das densidades foi possível caracterizar totalmente o plasma e compará-lo com outros plasmas naturais e artificiais. / In this work, an analysis of two ferritic stainless steel standards irradiated by nanosecond and femtosecond pulsed lasers was carried out. The temperature and electronic density of the plasma were determined by spectroscopic analysis of the emission from different atomic species, in different spectral ranges and integration gates. The temperatures were evaluated by two methods: Atomic Boltzmann plot and two line ratio. The results were compared in order to verify if the two line ratio method can agree to the results evaluated by the Boltzmann plot method. An agreement between the two methods was observed in the femtosecond generated plasma, otherwise there was no sufficient agreement in the nanosecond generated plasma. The electronic density of the plasma was determined by Stark broadening and the nanosecond generated plasma is denser than the femtosecond generated one. The densities evaluated under different integration gates were compared and the earliest gates were denser than the final ones. The plasma temperature and density can completely characterize the plasma and a comparison between these ablation related plasma and a comparison between them and other natural and artificial plasmas was performed.

Pas de résumé en français / One of the new challenges of conservation science is the development of field instrumentation to analyze works of art. In order to get the most information on the material, it is often necessary to perform complementary analyses by juggling different analytical techniques. This time-consuming drawback involves a difficulty to analyze the artwork on the same spot of the surface. However, some of spectroscopies have in common to use the same laser as excitation source and the collection of the emitted signal could be recorded by the same spectrometer. In this spirit, the aim of this research project is the development of a hybrid system in laboratory grouping together three analytical techniques (LIBS, LIF and Raman spectroscopy) in a single instrument. The relevance for combining these three spectroscopies is to identify a material (molecular and elemental analysis) without any preliminary preparation, regardless of its organic or inorganic nature, on the surface and in depth, without any surrouding light interference thanks to time-resolution. Such instrumentation would allow to characterize different materials from cultural heritage such as copper corrosion products and wall paintings organized in stratigraphic layers which are the example of applications in this work. A complete study on LIBS-LIF-Raman hybrid was carried out from conception to instrumental achievement, as well as automatic control to data fusion processings in order to elaborate a strategy of analysis according to the material and to be able to address conservation issues.

Diploma thesis presents the description of laser induced breakdown spectroscopy (LIBS) analytical method. The possibility to decrease LIBS detection limits using double pulse LIBS (DP-LIBS) is also detailed. Properties of laser induced plasma (LIP) are discussed. Thesis describes the optimisation process of DP-LIBS setup at laser spectroscopy laboratory of Faculty of Mechanical Engineering, Brno University of Technology. Optimisation was carried out for detection of chrome in steel with respect to detection limits and ablation crater size. Optimised DP-LIBS setup is appropriate for mapping chrome distribution in steel samples.

Laser-induced breakdown spectroscopy (LIBS) is an efficient tool for identification of elemental composition and characterization of materials. The concept of this technique is to focus a laser pulse of sufficiently high power on to a sample to create a plasma plume of atoms, ions, and molecules. The measurement of the resulting optical emission from these species provides the basis of the spectral analysis. Spectroscopic analysis of the plasma generated by Nd:YAG laser irradiation of wheat flour tortillas was carried out. A careful selection of spectral lines of Ca, Na and K which do not suffer from spectral interference was made. Among the spectral lines selected for analysis, the Na I 589.00 and 589.60-nm doublet lines were found to show the same intensity ratio values. A study on combustion was carried out with the use of LIBS. The main focus of this study was to compare results previously obtained using a rectangular slot burner with new results using a McKenna burner for equivalence ratios measurement in atmospheric premixed methane-air flames with ungated LIBS and also obtaining a temperature profile for our new burner. The Mckenna burner has a steady and less turbulent flame. Fortyive equivalence ratios were calculated. LIBS spectra of helium, argon and nitrogen were acquired using samples of pure gases at low pressures. The spectra from the three species showed continuum contributions which differ from one gas to the other. To better understand LIBS of gaseous samples, we have performed a study of the laser-induced plasmas in three gases, i.e., Ar, He, N2 and their mixtures. The evolution of plasma intensity and electron density, with time was studied at different laser pulse energies. Samples containing cerium, cesium and strontium were made with known concentrations and analyzed using laser-induced breakdown spectroscopy (LIBS). Powder samples are more challenging to analyze using LIBS than pellets. Spectra resulting from these samples under various experimental conditions were compared for possible interferences and other properties, placing particular interest in Ce II 418.65-nm, Cs I 852.11-nm and Sr I 460.73-nm atomic emission spectra lines because these were outstanding strong lines of these three aforementioned elements.

Laser-induced breakdown spectroscopy (LIBS) has been established as a rapid, in situ, and real-time spectroscopic analytical technique for material characterization. It is very handy for the study of all kinds of materials irrespective of their state. After being used for a Mars mission, LIBS has gained global attention and many scientific researches are investigating its applications. The main objective of this dissertation is to study the possibility of using laser spectroscopic sensing techniques for material characterization and if possible, to develop methodologies. Studying molecular emission spectra for elemental analysis is a relatively new trend in the spectroscopic field. Molecular emission from SrCl and SrO observed in LIBS spectra were analyzed and compared with atomic emission from Sr. Calibration models were developed using both molecular bands and atomic spectral peaks. The determination of nutritional elements in crops, vegetables, and fruits is very important to evaluate their nutritional status. The LIBS technique was applied to identify the nutritional elements present in cauliflower and broccoli, and to evaluate the difference between organic and conventional vegetables in terms of nutritional elements. Principal component analysis (PCA) and one-to-one comparison using Student's t-test were employed for discrimination between organic and conventional vegetable flowers. Early iron and steel production in the state of Pennsylvania (United States) mostly utilized blast furnaces that were operated by charcoal as a primary fuel, followed by anthracite, then coke. The process left behind a by-product known as blast furnace slag. Blast furnace slag, non-metallic in nature, appears to have various industrial applications. LIBS was used for the analysis of charcoal blast furnace slags and qualitative as well as quantitative analyses were demonstrated. To evaluate the possibility of using the LIBS technique to detect and quantify rare earth elements, three consecutive studies were executed. Firstly, pure oxides of six rare earth elements were studied and then real samples directly taken from natural ores were analyzed. In the third step, two rare earth elements (Eu and Yb) in aqueous solutions were studied by underwater LIBS and the pressure effect on the plasma emission is discussed.

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In this diploma thesis the differences between single pulse and double pulse laser induced breakdown spectroscopy (LIBS) methods are discussed. The time evolution of laser induced plasma (LIP) parameters, such electron density, plasma temperature, density of ions and atoms is shown. Selected methods for evaluation of plasma parameters (Boltzmann equation, Saha-Boltzmann equation etc.) are also stated. The theoretical bases of local thermodynamic equilibrium (LTE), which is necessary condition for using of previously stated methods for computation of plasma parameters, are discussed. Diploma thesis also contains the description of each component of our LIBS experimental set up and the way of their optimization. Presented theoretical advantages of DP LIBS method are demonstrated on results of experimental measurements of steel standards.

Laser-Induced Breakdown Spectroscopy (LIBS) is a method of analytical chemistry that provides a qualitative and quantitative analysis of a sample. The ablation process of a sample is fast and dynamic and the change of plasma in time and space is a question of a few microseconds. An examination that provides a good time and space resolution is necessary to understand better the physical processes. For this reason, the goal of this thesis is to design a basic optomechanic construction for this type of experiment. Furthermore, it is important to check the functionality of this design and to use it for a basic comparison between the spectroscopic and imaging data. Also, the time development of plasma will be observed under different experimental conditions. The goal of this thesis, in general, is to prove that the morphology of plasma is as it is described in available related literature.

The diploma thesis deals with the use of laser induced breakdown spectroscopy (LIBS) for detection of heavy metals traces, copper and lead, in aqueous solution of copper(II) sulphate pentahydrate and lead(II) ethanoate trihydrate. Results obtained by using single and double-pulse LIBS are compared. The theoretical section focuses on the issue of heavy metals and detection possibilities, describes the fundamental principle of LIBS technique and its modification for liquid analysis. The experimental section describes analyzed samples, the experimental apparatus, double-pulse technique, and method of spectral analysis. The moving breakdown model, which theoretically predicts optimal values of some experimental parameters, is explained briefly in section Optimalizácia. This model has been tested, however the results of experiments did not prove the theory. Furthermore, the experimental section reports the process and results of the optimization of all key measurement parameters and obtaining limits of detection from calibration curves.