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Laser Induced Breakdown Spectroscopy (LIBS) which is used to determine the elemental content of various samples, inspects the emission spectroscopy of samples of interest for searching certain elements or identifying the unknown content. In this study, spectroscopic analyses of various kinds of metals, namely, Cu, Fe, Mo, Ti, W, some compounds such as CuBe, ZnSe, ZnS, GaSe, some semimetals like Si, Ge and even gases were investigated by means of a compact-commercial portable LIBS system and an independently constructed experimental set-up consisting of a single pulse system and various kinds of double pulse configurations using Nd:YAG lasers. The contributions of this thesis to the LIBS community can be classified into two main groups- which are experimental and code development. One of the experimental contributions was the investigation of the different crystal surfaces of silicon in which dangling bond density were taken into account for a more precise comparison of atomic emissions. The second experimental contribution was the polarization experiments by which polarization dependency, to some extent, was demonstrated. The third and final one was the orthogonal double pulse configuration with a 45 o incidence angle for both lasers in opposite directions by which it was shown that the positioning becomes straightforward yielding the desired reproducible results. The second major contribution was to develop a basic code for analyzing the experimental data more accurately. In conclusion, by means of the different experimental approaches, factors relating to the enhancement in intensity were investigated and as a result of developing the code, flexibility in upgrading the constraints of element searching was obtained and the updating of the database was accomplished.

No / In this paper, molecular modelling was used to investigate the nature of probe/surface interactions during the analysis of Dß-mannitol using inverse gas chromatography (IGC). IGC was used to experimentally measure the dispersive components of surface free energy () and the specific components of free energy of adsorption () of Dß-mannitol by calculating the retention time of non-polar (n-alkanes) and polar (tetrahydrofuran and chloroform) probes, respectively. The results showed that Dß-mannitol surface is acidic in nature because the basic probe had more interaction with the surface as compared to acidic probe. Cerius2 software package was used to model the two morphologically important surfaces, which showed the presence of surface hydroxyl groups. Molecular dynamics simulations were performed in Cerius2 to model the adsorption of the same probes (n-alkanes, tetrahydrofuran and chloroform) on the Dß-mannitol surfaces. The adsorption energies calculated from the simulation showed a close match to those determined experimentally. The calculated values are slightly higher for all probes except chloroform, but as a single perfect crystal was modelled without considering the effect of impurities, solvent and other physical factors this is not unexpected.

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