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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 266-275 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The upconversion of infrared radiation into green and red fluorescence has been studied for Er3+ and Yb3+ ions in BaF2/ThF4 fluoride glass over a wide temperature range and several dopant concentrations. At room temperature an upconversion efficiency of 3.3×10−5 has been obtained for the green emission from the glass with 1 mol % ErF3 and 19 mol % YbF3 pumped by 973-nm radiation with intensity of 16.5 mW/cm2. For an absorbed intensity of 10 W/cm2 the efficiency for green upconversion emission is predicted to be 2%. Radiative transition rates for the excited states of Er3+ were calculated using Judd–Ofelt theory and intensity parameters obtained from measured integrated absorption coefficients. The calculated values of the multiphonon relaxation and the upconversion fluorescence intensity, obtained from the rate equation model of Wright, are discussed in light of the experimental results.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1117-1122 
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The enthalpy changes during structural relaxation or physical aging of a 58ZrF4-33BaF2-5LaF3-4AlF3 (ZBLA) glass during annealing well below the glass-transition temperature have been studied using differential-scanning calorimetry at several sub-Tg temperatures. Substantial relaxation within the course of several hours was detected at temperatures as low as sixty degrees below Tg (585K). The relaxation process is extremely nonlinear and self-retarding. The time dependence of the enthalpy during the initial stages of annealing was modeled approximately using the Narayanaswamy-Tool approach. The structural-relaxation parameters obtained from this fit were used to predict rates of physical aging for rapidly cooled ZBLA glass at temperatures close to ambient.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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