• A N Pandey

      Articles written in Pramana – Journal of Physics

    • Electron diffraction data as a constraint in the determination of force field of thallous halide dimers

      D K Sharma U P Verma A N Pandey V Kumar

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      Electron diffraction data have been used as a constraint in the determination of force field for Tl2F2 having planar rhombic structure. The L-F approximation method, recently given by us, has also been applied to evaluate force constants for thallous halide dimers,e.g. T12F2 and T12Cl2. The results have been compared with the available experimental data in order to check the validity of the present work. It is concluded that non-bond experimental mean amplitudeU1...Tl for Tl2F2 is capable of fixing the force field and L-F approximation gives reasonably good force fields for the two thallous halide dimers now under study.

    • Some optical properties of rare earth (Dy, Nd and Sm) activated ZnO phosphors

      S Bhushan Balakrishna Rao Kaza A N Pandey

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      Some rare earth (Dy, Nd and Sm) doped ZnO electroluminors have been prepared in vacuum (1 torr) and their photo (PL) and electroluminescence (EL) spectra investigated at room temperature at different concentrations of rare earth (RE) ions. Compared to the spectra of undoped ZnO, these spectra consist of the same bands shifted either towards low or high energy side and the intensity of high energy band is decreased while that of low energy band is enhanced. In any case no additional band or line was observed. The experimental results have been explained on the basis of donor-acceptor pair model of recombination process where donor levels are due to RE ions and the acceptors are the luminescent centres of undoped ZnO electroluminors. The mechanism of excitation is of acceleration-collision type.

    • Brightness waves of electroluminescence in ZnO:Nd electroluminor

      S Bhushan Balakrishna Rao Kaza A N Pandey

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      Brightness waves due to sinusoidal excitations for ZnO:Nd electroluminor have been investigated for a temperature range 93°K to 363°K. During each cycle of excitation it consists of two primary waves each associated with a secondary wave, which grow and disappear twice in this temperature range. These results have been discussed in terms of existing models.

    • Photoacoustic determination of energy band gap of semiconductors

      R S Ram O M Prakash A N Pandey

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      Semiconducting materials are employed in the fabrication of a number of semiconductor devices and opto-electronic detectors etc depending on their properties, state of purity and perfection and energy band gap values. In the present study, a latest and novel photoacoustic spectroscopic technique has been employed for the determination of energy band gap of some semiconductors namely CdS, CdSe, CdTe, ZnS, ZnO, Se and Si in the powder form. Values obtained have been compared with those reported by conventional methods.

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