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Browsing Department of Physics by Subject "calibration"

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    Mossbauer Spectroscopy of Tin Compounds.
    (Obafemi Awolowo University, 1985) Arua, Awa Eke; Osadebe, F. A. N.
    The Mossbauer spectrometer has been used in the transmission geometry to measure the isomer shifts and quadrupole splitting of tin and some of its inorganic compounds. The spectrometer has a Moire interferometer for absolute velocity calibration and the velocity data are fitted to a polynomial by the method of least squares. As a check on the velocity calibration, a natural iron foil absorber has been used. The ratio of the g-factors extracted from the iron data is in agreement with published values. The Mossbauer spectral data has been fitted with a sum of Lorentzians and the isomer shift and quadrupole splitting values obtained from these fits are in good agreement with published ones. Using s-electron densities Calculated from relativistic Hartree-Fock method for the various oxidation states of tin the fractional change in nuclear charge radius ΔR/R following a gamma transition has been calculated as (+2.05 ± 0.17) x 10-4. This is in good agreement with published values. From molecular orbital calculations, a configuration of 5s1..25p 2..8 has been suggested for α-tin. No equivalent data exists for β-tin. However, since the isomer shift is directly proportional to the s-electron density at the nuclear site, the measured isomer shift value has been used to suggest a configuration of 5s1.42 5p2.8 for β-tin. This is consistent with the saner shift values for the two allotropes of tin.
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    Phofluorescence Lifetime Measurement by Single Photon Counting
    (Obafemi Awolowo University, 1985) Aweda, Moses Adebayo; Aladekomo, J. B.
    A fluorescence lifetime measuring instrument in the nanosecond time range has been assembled using components from the ORTEC, EMI, TEKTRONIX, BRANDENBURG AND CAMBERRA. The fluorescence emmission spectra of two aromatic hydro-carbons (naphthalene and pyrene) were measured for identification and proper classification. The lifetime measuring instrument was calibrated and tested with 1µg/ml solution of quinine sulphate in. 0.05M sulphuric acid. A value of 21.50 ns was obtained for the fluorescence lifetime of quinine sulphate. The fluorescence lifetimes of naphthalene and pyrene were then determined with this system using four different concentration of each sample. A vacuum system was also constructed for removing the dissolved oxygen in these aromatic hydrocarbons. After degassing the measurement was repeated for each sample. The monomer fluorescence lifetime of 437.50 ns was obtained for naphthalene while 577.02 ns was obtained for pyrene.