Navegando por Palavras-chave "LiF"

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    Confocal and atomic force microscopies of color centers produced by ultrashort laser irradiation in LiF crystals
    (Amer Inst Physics, 2008-01-01) Courrol, Lilia Coronato [UNIFESP]; Martinez, Oscar; Samad, Ricardo Elgul; Gomes, Laercio; Ranieri, Izilda Marcia; Baldochi, Sonia Licia; Freitas, Anderson Zanardi de; Vieira Junior, Nilson Dias; Wetter, N. U.; Frejlich, J.; Universidade Federal de São Paulo (UNIFESP)
    We report properties of the spatial and spectral distribution of color centers produced in LiF single crystals by ultrashort high intensity laser pulses (60 fs, 10 GW) using confocal spectral microscopy and atomic force microscopy. We could identify a large amount of F centers that gave rise to aggregates such as F-2, F-4, F-2(+) and F-3(+) distributed in cracked shape brownish areas. We have taken a 3D image using confocal microscopy of the sample (luminescent image) and no difference is observed in the different planes. The atomic force microscopy image clearly shows the presence of defects on the modified surface. The formation of micrometer or sub-micrometer voids, filaments and void strings was observed and related to filamentation process.
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    Determination of a dose-like curve for active colour centres produced in LiF single crystals by ultrashort high intensity laser pulses and a preliminary investigation of their spectral and spatial properties by confocal and atomic microscopies
    (Iop Publishing Ltd, 2008-10-01) Courrol, L. C. [UNIFESP]; Samad, R. E.; Martinez, O. E.; Gomes, L.; Ranieri, I. M.; Baldochi, Sonia Licia; Freitas, A. Z. de; Vieira Junior, N. D.; Universidade Federal de São Paulo (UNIFESP); IPEN CNEN SP; Univ Buenos Aires
    In this paper, the spatial and spectral properties of colour centres produced in LiF single crystals by ultrashort high intensity laser pulses are reported. the emission spectra of the centres were measured conventionally and also by confocal microscopy. A large amount of F centres that gave rise to aggregates such as F(2), F(4), F(2)(+) and F(3)(+) could be identified, showing a microscopic homogeneous distribution. the coloured surfaces were also spatially characterized by atomic force microscopy, and the images show the presence of defects on the modified surface. the formation of micrometric and sub-micrometric structures was observed and related to filamentation processes.
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    Spectroscopy of the gamma and X ray leakage radiation from the built-in sources of a Riso TL/OSL reader
    (Elsevier B.V., 2014-12-01) Umisedo, Nancy K.; Kuenzel, Roseli [UNIFESP]; Okuno, Emico; Yoshimura, Elisabeth M.; Malthez, Anna Luiza M. C.; Freitas, Marcelo B. [UNIFESP]; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP); Universidade Estadual de Campinas (UNICAMP)
    In this work we evaluate the intensity and the spectral shape of the leakage radiation from the built-in beta and alpha sources of a Riso TL/OSL reader. LiF (TLD-100), fluorite-based pellets and Al2O3:C detectors were used in order to determine the dose rate delivered to the dosimeters when the sources are closed. the leakage spectra under both alpha and beta sources were registered with a CdTe semiconductor detector. the spectrum measured under the beta source shows the X-ray beam generated by the interaction of the beta particles with the lead used to shield the source. Besides, the 59.4 keV gamma ray from Am-241 was registered under the alpha source. Dose rates from 50 to 100 mu Gy/h were obtained for the dosimeter positions in the turntable under the beta and the alpha sources with the luminescent dosimeters. (C) 2014 Elsevier B.V. All rights reserved.