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[en] Various types of vacuum ultraviolet continuum sources are critically reviewed. Their relative advantages and disadvantages are discussed. Detailed experimental procedures for the excitation of the rare gas continua (He, Ne, A, Kr and Xe) are presented. Theory of production of the rare gas continua is discussed. A number of emission bands of Kr2 is observed in the present studies for the first time. The mechanism of production of the helium continuum in the 600 - 11000A region is presented. The great potential for the exploitation of the helium continuum in 1100 -40000A region is indicated. (author)
[en] In the electronic spectrum of silicon monotelluride which has been produced in microwave discharges through sealed tubes, a large number of new bands belonging to the A1Π-X1Σ+ (3100-3900 A) and the E1Σ+-X1Σ+ system (2800-3100A) of Si130Te has been observed. The vibrational structure analyses of these band systems have resulted in the determination of improved vibrational constants in all the three electronic states involved in these transitions. An error in the previous determination of the vibrational constants of the E1Σ+ state has been corrected. An upper limit for the dissociation energy of the silicon monotelluride has been determined to be 40,000 cm-1. (author). 8 refs., 3 ta b
[en] Isotope shift data of the visible (3500-6200 A) and the ultraviolet (2100-2600 A) bands of the molecules 28Si32S and 28Si34S confirm the vibrational assignments proposed by Thomas (Thesis. Oxford Univ. (1947)) and Bredohl et al (J. Phys. B.; 8: L259 (1975)) and further show that both the groups of bands belong to the E 1Σ+-X1Σ+ system of the SiS molecule. The vibrational assignments of the 2500-3900 A bands of the D 1PI-X1Σ+ system are also confirmed from the present studies of the emission spectra of the isotopic molecules. (author)
[en] Six mutants obtained by gamma-ray irradiation and post-irradiation chemical treatment were selected on the basis of seed size, branching pattern and period of maturity and analysed for seed yield, oil content, protein content and fatty acid composition. Increase in the seed size was associated with an increase in protein content as well as erucic acid content in oil but not with oil content. As compared to controls, the increase in erucic acid content was found in all the mutants. (author)
[en] Bi-, Pb-, Sb-, Sn-, Bi/Yb-, Pb/Yb-, Sb/Yb- and Sn/Yb-co-doped germanate glasses were prepared and optically characterized. All these glasses doped with different 6p (Bi, Pb) and 5p (Sn, Sb) ions have shown broadband near-infrared (NIR) fluorescence with different excitation wavelengths and the lifetime of metastable level is about 37 μs. Different oxidation states and point defect optical centres caused by the presence of 6p (Bi, Pb) and 5p (Sn, Sb) ions are proposed for the explanation of NIR emission in these laser materials.
[en] In this paper, we report on the phosphosilicate glass membranes doped with a mixture of titanium oxide (TiO2) and zirconium oxide (ZrO2) for their applicability in low-temperature H2/O2 fuel cell electrolytes. Measurements concerning x-ray diffraction, optical absorption/transmission, Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric and differential thermal analysis, impedance and permeability studies as well as electrochemical analysis were carried out. The specific surface area and pore size distributions were described by the Brunauer-Emmett-Teller method and the average pore size found to be approximately in the range 2.1-2.3 nm for all composite membranes. The FTIR analysis displayed a maximum intensity in the range 1000-1300 cm-1, indicating the presence of Si-O-Si bonds in all the studied composite glass membranes. A high proton conductivity of 9.3 x 10-3 S cm-1 was obtained for the 83SiO2-5P2O5-2TiO2/10ZrO2 (mol%) composite at 80 0C under 90%RH, while for the 83SiO2-5P2O5-2ZrO2/10TiO2 (mol%) composite the conductivity was only 7.1 x 10-3 S cm-1 under the same conditions. The permeability was measured for a hydrogen flow background and was found to decrease from 1.77 x 10-11 to 5.95 x 10-12 mol cm-1 s-1 Pa-1 for 2TiO2/10ZrO2 (mol%) doped glass composite, and for the 2ZrO2/10TiO2 (mol%) composite the permeability decreases from 1.35 x 10-11 to 4.52 x 10-12 mol cm-1 s-1 Pa-1 as the temperature increases from 30 to 110 0C. A sample (83SiO2-5P2O5-2TiO2/10ZrO2 (mol%)) was selected as an electrolyte for the H2/O2 fuel cell test and yielded the maximum power density value of 10 mW cm-2 using electrochemical measurements at 30 0C under relative humidity atmosphere.
[en] Oxyfluoride aluminosilicate glasses in the composition of 50SiO2-20Al2O3-20LiF-10GdF3-0.5TmF3-xYbF3 (x = 0, 1.0, 2.5, 5, 7.5, 10, 15, 20, 25 and 30 mol%) have been prepared to study their thermal and optical properties. From the differential thermal analysis measurements, glass transition temperatures and onset crystallization temperatures have been evaluated and from them glass stability factors were calculated. Glass stabilities decreased gradually with fluoride content increment in all the studied glasses. The photoluminescence and decay measurements have also been carried out for all these glasses. In these glasses, an efficient near infrared quantum cutting with optimal quantum efficiency approaching 187% has been demonstrated, by exploring the co-operative downconversion mechanism from Tm3+ to Yb3+, with 467 nm (Tm3+ : 3H6 → 1G4) excitation wavelength. These glasses are promising materials to achieve high efficiency silicon based solar cells by means of downconversion in the visible part of the solar spectrum
[en] In this paper, we present the spectral results of Dy3+ and Pr3+ (1.0 mol%) ions doped Bi2O3-ZnF2-B2O3-Li2O-Na2O glasses. Measurements of X-ray diffraction (XRD), differential scanning calorimetry (DSC) profiles of these rare-earth ions doped glasses have been carried out. From the DSC thermograms, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures have been evaluated. The direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. The emission spectrum of Dy3+:glass has shown two emission transitions 4F7/2→6H15/2 (482 nm) and 4F7/2→6H13/2 (576 nm) with an excitation at 390 nm wavelength and Pr3+:glass has shown a strong emission transition 1D2→3H4 (610 nm) with an excitation at 445 nm. Upon exposure to UV radiation, Dy3+ and Pr3+ glasses have shown bright yellow and reddish colors, respectively, from their surfaces
[en] In this paper, we present the absorption and photoluminescence properties of Pr3+, Sm3+ and Dy3+-doped transparent oxyfluoride alumino-silicate glass ceramics and Sm3+ and Dy3+-doped oxyfluoride germanate glasses. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of these glasses have been carried out, to confirm their structure and thermal stability. These glasses or glass ceramics have shown strong emission and absorption bands in visible and near-infrared (NIR) region. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters (Ω2, Ω4 and Ω6) have been calculated for all the studied ions. Compared to Pr3+, Sm3+ and Dy3+ doped glasses, their respective glass ceramics have shown stronger emissions due to LiGdF4 crystalline phase in alumino-silicate glass ceramics. For Pr3+ doped glass and glass ceramic, emission bands centered at 527 nm(3P0→3H5), 610 nm(3P0→3H6), 640 nm(3P0→3F2), 678 nm(3P1→3F3), 702 nm(3P0→3F3) and 721 nm(3P0→3F4) have been observed with 445 nm(3H4→3P2) excitation wavelength. Of them, 640 nm(3P0→3F2) has shown bright red emission. Emission bands of 4G5/2→6H5/2 (562 nm), 4G5/2→6H7/2 (598 nm), 4G5/2→6H9/2 (644 nm) and 706 nm(4G5/2→6H11/2) for the Sm3+: glass and glass ceramic, with excitation at 6H5/2→4F7/2 (402 nm) have been recorded. Of them, 4G5/2→6H7/2 (598 nm) has shown a bright orange emission. With regard to the Dy3+: glass and glass ceramic, a bright fluorescent yellow emission at 576 nm(4F9/2→6H13/2) and blue emission at 485 nm(4F9/2→6H15/2) have been observed, apart from 4F9/2→6H11/2 (662 nm) emission transition for glass ceramic with an excitation at 388 nm(6H15/2→4I13/2+4F7/2) wavelength. For germanate glasses, emission bands of 4G5/2→6H5/2 (564 nm), 4G5/2→6H7/2 (601 nm), 4G5/2→6H9/2 (644 nm) and 705 nm(4G5/2→6H11/2) for the Sm3+: glass, with an excitation at 6H5/2→4F7/2 (401 nm) have been recorded. Of them, 4G5/2→6H7/2 (601 nm) has shown a bright orange emission. With regard to the Dy3+: glass, a bright fluorescent yellow emission at 576 nm(4F9/2→6H13/2) and blue emission at 482 nm(4F9/2→6H15/2) have been observed, apart from 4F9/2→6H11/2 (661 nm) emission transition with an excitation at 386 nm(6H15/2→4I13/2+4F7/2) wavelength. The stimulated emission cross-sections of all the emission bands of Pr3+, Sm3+ and Dy3+: glasses and glass ceramics have been computed based on their measured full-width at half maxima (FWHM, Δλ) and measured lifetimes (τm).
[en] In this paper, we present the photoluminescence properties of Eu3+, Tb3+ and Tm3+-doped oxyfluoride alumino-silicate glasses and glass ceramics. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of these glasses have been carried out, to confirm their structure and thermal stability. Compared to Eu3+, Tb3+ and Tm3+-doped glasses, their respective glass ceramics have shown stronger emissions due to the presence of LiGdF4 crystalline phase. For Eu3+-doped glass and glass ceramics, five emission bands centered at 578 nm (5D0 → 7F0), 592 nm (5D0 → 7F1), 614 nm (5D0 → 7F2), 652 nm (5D0 → 7F3) and 698 nm (5D0 → 7F4) have been observed with 394 nm (5D0 → 7L6) excitation wavelength. Of them, 614 nm (5D0 → 7F2) has shown bright reddish-orange emission. With regard to the Tb3+-doped glass and glass ceramic, four emission bands centered at 491 nm (5D4 → 7F6), 545 nm (5D4 → 7F5), 587 nm (5D4 → 7F4) and 622 nm (5D4 → 7F3) have been observed with an excitation at 377 nm (3F6 → 5G6) wavelength. Of them, 545 nm (5D4 → 7F5) has shown bright green emission. Emission bands of 1G4 → 3F4 (650 nm) and 3F3 → 3H6 (708 nm) transitions for the Tm3+:glass and glass ceramic, with an excitation at 3H6 → 1G4 (469 nm) have been observed. The stimulated emission cross-sections of all the emission bands of Eu3+, Tb3+ and Tm3+:glasses and glass ceramics have been computed based on their measured full-width at half maximum (FWHM, Δλ) and lifetimes (τm).