Masters Degrees (Physics)

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Browsing Masters Degrees (Physics) by Subject "Absorption spectroscopy"

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    Development of VUV tunable laser spectroscopy techniques for characterizing calcium fluoride
    (Stellenbosch : Stellenbosch University, 2014-12) Matindi, Tresor; Steenkamp, Christine M.; Rohwer, Erich G.; Stellenbosch University. Faculty of Science. Dept. of Physics.
    ENGLISH ABSTRACT: The large band gap (approximately 11.5-12.1 eV) and high transmission of calcium fluoride (CaF2) crystal in the ultraviolet (UV) and vacuum ultraviolet (VUV) region makes it an important material for optics for laser applications in UV. However, CaF2 degrades during long exposure to UV irradiation due to defect generation. The formation of selftrapped excitons (STE) is considered the first step in defect generation. In this project the possibility of observing STE states in CaF2 using a narrow bandwidth tunable VUV laser source is investigated. This is the first spectroscopy study of an alkaline earth fluoride using VUV tunable laser radiation instead of a fixed wavelength laser. The use of a VUV tunable laser source has potential for determining the energies of the STE states, which are unknown. Our main objective is addressed by developing techniques to measure absorption spectra of pure and doped CaF2 samples, using a VUV scanning monochromator and a tunable VUV laser, and by doing a literature study. The results obtained with the scanning monochromator show absorption features in 126-180 nm range of all our samples. These vary for different samples and correlate with information from the supplier on the samples’ fluorescence spectra. Total absorption of the VUV light by CaF2 in the 115-126 nm range is observed. With the narrow bandwidth tunable laser light, absorption spectra were obtained in the range of 143-146.7 nm of all our CaF2 samples. No significance peaks which can be related to the STE states in CaF2 were observed in the VUV laser absorption spectra, but the results are valuable to improve the technique. The conclusion is that either a different spectral range or fluorescence detection can be investigated in future.