• Volume 16, Issue 4

      April 1981,   pages  273-367

    • Mossbauer study of ferrite systems CoxMn1−xFe2O4 and NixMn1−xFe2O4

      V K Singh N K Khatri S Lokanathan

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      Mössbauer spectra of CoxMn1−xFe2O4 and NixMn1−xFe2O4 ferrites withx values ranging from 0·1 to 0·8 in steps of 0·1 have been recorded at room temperature. All spectra exhibit well-defined Zeeman hyperfine patterns. It has been observed that hyperfine field at Fe3+ nucleus increases more rapidly by nickel substitution than by cobalt substitution. This has been explained in terms of exchange interactions and cation distribution in the spinels. Hyperfine fields, isomer shifts and quadrupole splittings have been determined.

    • X-ray studies on the thermal expansion of copper indium disulphide

      P Kistaiah Y C Venudhar K Sathyanarayana Murthy Leela Iyengar K V Krishna Rao

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      The lattice parameters of the compound copper indium disulphide (CuInS2) have been measured by x-ray diffraction. The data have been used to evaluate the coefficients of thermal expansion, perpendicular and parallel to the principal axis. The thermal expansion studies revealed the anisotropy between the axial expansion coefficients having a larger coefficient of expansion alonga axis than that alongc axis. The anisotropic thermal expansion of this compound is interpreted in terms of the thermal expansion of the Cu-S and In-S bonds.

    • ZnO: Cu, Sn electroluminescent phosphor

      R C Maheshwari M H Khan

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      The a.c. electroluminescent characteristics of ZnO:Cu, Sn powder phosphor have been investigated in audio frequency range. A simple preparative method for this phosphor has been described. The detailed variation of light output during one cycle of the applied sinusoidal voltage has been studied and discussed. In addition to the two primary peaks, the two secondary peaks have also been observed in each cycle of the applied field. The voltage and frequency dependence of the time-averaged electroluminescent brightness have been found to follow the Alfrey-Taylor relation over a wide range of frequencies. The constants of this relation have been determined. The spectral energy distribution of this phosphor shows that the peak-shift depends upon the a.c. frequency and is independent of the magnitude of applied field.

    • Overall values of conventional discrepancy indices for crystals with heavy atoms. Part II. Results for monoclinic and orthorhombic crystals when the heavy-atom part alone constitutes the model

      S Parthasarathy M N Ponnuswamy

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      Theoretical expressions of 〈yN〉, 〈|yN − σ1yPc |〉 and 〈|yN2σ12 (yPc)2|〉 (whereyN andyPc are the normalized structure amplitudes of the structure and the model respectively) are derived in terms of the heavy atom contributionσ12 for monoclinic and orthorhombic crystals containing a few (i.e., 1 or 2) heavy atoms of the same kind per asymmetric unit by taking the heavy atom part alone as the model. Results are obtained for both the related and unrelated cases. The local values of 〈yN〉 and 〈|yNn − σ1n (yPc)n|〉, (n=1, 2) calculated from these expressions can be used to calculate the overall values of the conventionalR-indicesR(F) andR(I) for the related and unrelated cases. These overall values could be used to check the correctness of heavy atoms located in the structure.

    • Chemical ordering in As-Se glasses: X-ray absorption edge and XPES studies

      K J Rao R Mohan P R Sarode M S Hegde

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      X-ray absorption edge and X-ray photoelectron spectroscopic studies of As-Se glasses seem to support a chemical ordering model.

    • Photocurrent measurement in chemically deposited CdS: Li films

      A G Shikalgar S H Pawar

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      The dependence of photocurrent on the light intensity in CdS:Li films formed by chemical bath deposition technique is studied. The superlinearity observed is explained on the basis of increased lifetime of the photoexcited electron. The effect of oxygen adsorption in the film surface on the lifetime of the electron is studied.

    • The radio frequency conductivity of some aliphatic alcohols at different temperatures

      R Ghosh I R A Chaudhury

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      Activation energies for viscous flow and conductivity are computed from experimental values of RF conductivity (frequency 400 kHz) at different temperatures for eight polar liquids. It is observed that for aliphatic alcohols the activation energy for conductivity is greater than that for viscous flow. However, their ratio is slightly greater than unity and is different for different alcohols whereas for nonassociating polar liquids the ratio is almost equal to unity. The dependence of conductivity on viscosity for the liquid alcohols does not follow the Walden’s law but can be well represented by Adamczewskis relation.

    • Rotational measurements on (4–6), (5–7) bands of CN (B2Σ+ − X2Σ+) transition

      M R Gorbal M I Savadatti

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      Rotational analysis of (4–6), (5–7) bands of CN (B2Σ+X2Σ+) transition extending to highJ and emitted from the chemiluminescent reaction involving pink afterglow of nitrogen is presented.

    • Convergent polynomial expansion, energy dependence of slope parameters, scaling hypothesis and predictions forπ±p andK+p scattering

      N Giri M K Parida

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      A phenomenological representation for differential cross-section recently proposed using Mandelstam analyticity and convergent polynomial expansion (CPE) which has been found to be successful in describing scaling of the differential cross-section-ratio data for several elastic diffractive and inelastic nondiffractive processes is used to analyse the energy dependence of the slope-parameter data at high energies, extrapolate the slope parameter and predict the differential cross-section ratio as a function of |t| at higher energies forπ±pndK+p scattering. Following the method of Hansen and Krisch it is found that, in spite of the existence of rather widely varying data points for nearbys values, a more systematic trend in the energy dependence of the slope parameter emerges when a statistical average of the existing high-energy data is used. Extrapolating the fits to the average data ontos → ∞ provides strong evidence in favour of a model-independent result that asymptotically theπ±p slopes may be equal. There is also a strong indication to the effect that each of these two slopes may be equal to theK+p slope fors → ∞. Using the scaling curves generated by the existing data on differential cross-section ratio and extrapolated values of the slope parameter, the differential cross-section ratio for each of the three processes is predicted as a function of |t| for higher energies.

    • Mass relations for heavy mesons

      D Mishra C V Sastry

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      In a non-relativistic quark model, by parametrizing the quark-antiquark potentials, some mass relations have been obtained. Algebraic expressions for the masses of higher flavour meson isosinglets have been given in terms of the meson masses of lower symmetries. Hallock and Oneda’s contention of two types of sumrules for nonet mesons in SU(3) has been examined and the possibilities of such different sum-rules of this type in SU(4) and SU(5) have been explored.

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