No description available.

Thesis (Ph.D.)--Ohio University, June, 2007. / Includes bibliographical references (leaves 186-191)

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 73-77).

Thesis (Ph. D.)--University of Alabama at Birmingham, 2010. / Title from PDF t.p. (viewed July 20, 2010). Additional advisors: Mian M. Abbas, Renato P. Camata, Sergey B. Mirov, Thomas M. Orlando. Includes bibliographical references (p. 111-117).

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Hot white dwarf stars are the ideal probe for a relationship between the fine-structure constant and strong gravitational fields, providing us with an opportunity for a direct observational test. We study a sample of hot white dwarf stars, combining far-UV spectroscopic observations, atomic physics, atmospheric modelling, and fundamental physics in the search for variation in the fine structure constant. This variation manifests as shifts in the observed wavelengths of absorption lines, such as quadruply ionized iron (FeV) and quadruply ionized nickel (NiV), when compared to laboratory wavelengths. Berengut et al. (Phys. Rev. Lett. 2013, 111, 010801) demonstrated the validity of such an analysis using high-resolution Space Telescope Imaging Spectrograph (STIS) spectra of G191-B2B. We have made three important improvements by: (a) using three new independent sets of laboratory wavelengths; (b) analysing a sample of objects; and (c) improving the methodology by incorporating robust techniques from previous studies towards quasars (the Many Multiplet method). A successful detection would be the first direct measurement of a gravitational field effect on a bare constant of nature. Here we describe our approach and present preliminary results from nine objects using both FeV and NiV.

Orientador: Flávio Caldas da Cruz / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-30T20:50:45Z (GMT). No. of bitstreams: 1 IngaCaqui_MarvynWilliam_M.pdf: 57466489 bytes, checksum: e14e1adbe90a64e5b5e7ee380f180702 (MD5) Previous issue date: 2016 / Resumo: Neste trabalho desenvolvemos uma montagem óptica para realizar espectroscopia de alta sensibilidade através de medidas do tempo de decaimento da luz em uma cavidade óptica contendo uma amostra transparente (ring-down time spectroscopy). Usando um laser contínuo de comprimento de onda único em S32nm e uma cavidade de finesse moderada (16500), optamos por explorar o uso deste sistema para análise de amostras líquidas ou sólidas, ao invés do uso tradicional em espectroscopia de gases. Para isto utilizamos uma cubeta comercial intracavidade, com faces orientadas em ângulo de Brewster, para estudo de amostras líquidas. Uma análise das perdas residuais por reflexão nas faces foi realizada a fim de extrair o coeficiente de absorção do líquido. Demonstramos também o uso deste sistema para medidas de pequenos coeficientes de absorção de sólidos transparentes / Abstract: In this work, an experimental optical setup for high sensitivity ring-down time spectroscopy was developed. This is based on measurements of the light decay time in an optical cavity containing a transparent sample. Using a continuous-wave, single-wavelength laser at 532 nm and an optical cavity of moderate finesse (16500), we opted for exploring this system for analysis of liquid and solid samples, instead of the traditional use in gas spectroscopy. For this, an intracavity commercial cuvette with faces oriented at Brewster's angle was used for the study of liquid samples. An analysis of the limitations arising from the residual losses by reflection on the faces was carried out, in order to extract the absorption coefficient of the liquid. The usefulness of this system for measurements of the small absorption coefficients of transparent solids was also demonstrated / Mestrado / Física / Mestre em Física / 1186373/2013 / CAPES

We present the dielectric function of a bcc-In2O3 thin film in the wide spectral range from nearinfrared to vacuum-ultraviolet and for temperatures 10 K–300K, determined by spectroscopic ellipsometry. From the temperature dependence of electronic transition energies, we derive electron-phonon coupling properties and found hints that the direct parabolic band-band transitions involve In-d states. Further we discuss possible excitonic contributions to the dielectric function.

We determined the dielectric function of the alloy system (InxGa1−x)2O3 by spectroscopic ellipsometry in the wide spectral range from 0.5 eV to 8.5 eV and for In contents ranging from x = 0.02 to x = 0.61. The predicted optical transitions for binary, monoclinic β-Ga2O3, and cubic bcc-In2O3 are well reflected by the change of the dielectric functions’ lineshape as a function of the In content. In an intermediate composition range with phase-separated material (x ≈ 0.3…0.4), the lineshape differs considerably, which we assign to the presence of the high-pressure rhombohedral InGaO3-II phase, which we also observe in Raman experiments in this range. By model analysis of the dielectric function, we derived spectra of the refractive index and the absorption coefficient and energy parameters of electronic band-band transitions. We discuss the sub-band gap absorption tail in relation to the influence of the In 4d orbitals on the valence bands. The data presented here provide a basis for a deeper understanding of the electronic properties of this technologically important material system and may be useful for device engineering.