• Volume 11, Issue 1

      July 1978,   pages  1-117

    • Algebraic aspects of the wigner distribution in quantum mechanics

      N Mukunda

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      The algebraic structure underlying the method of the Wigner distribution in quantum mechanics and the Weyl correspondence between classical and quantum dynamical variables is analysed. The basic idea is to treat the operators acting on a Hilbert space as forming a second Hilbert space, and to make use of certain linear operators on them. The Wigner distribution is also related to the diagonal coherent state representation of quantum optics by this method.

    • Second order phase transition in two dimensional sine-Gordon field theory—Lattice model

      K Babu Joseph V C Kuriakose

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      Two dimensional sine-Gordon (SG) field theory on a lattice is studied using the single-site basis variational method of Drell and others. The nature of the phase transition associated with the spontaneous symmetry breakdown in a SG field system is clarified to be of second order. A generalisation is offered for a SG-type field theory in two dimensions with a potential of the from [cosn(√λ/m)ϕ−1].

    • Crystal structure of 1-amino-2-phenyl benzocycloheptanol hydrobromide monohydrate

      Vasantha Pattabhi

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      Crystals of 1-amino 2-phenyl benzocycloheptanol hydrobromide monohydrate are orthorhombic witha=6·927(17),b=30·947(40),c=30·990(40) Å,z=16 and the space group is Iba2.ρ=1·41 gm/ccρcal=1·403 gm/cc,μ for CuKα=37.06 cm−1. The structure was solved by heavy atom method using three dimensional x-ray intensity data and refined by block diagonal and full matrix least squares method to anR-index of 0·106. The structure is stabilised by a number of hydrogen bonds of the type N-H…O, O-H…Br, N-H…Br. The heptane rings in this molecule are in chair conformation.

    • Enhanced isospin dependence of the empirical particle-hole effective interaction

      D P Ahalpara K H Bhatt

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      The separation betweenT=0 andT=1 centroids of the empirical effective interaction is fairly large for the (d32/−1f7/2)JT particle-hole interaction as compared to nearby (f7/2)2JT and (d5/2)2JT particle-particle interactions. This interesting feature of the empirical effective interaction is shown to arise as a consequence of renormalization of the effective interaction as one truncates the configuration space from (sd)−1(fp)1 to (d32/−1f7/2) and from (fp)2 and (sd)2 configurations to (f7/2)2 and (d5/2)2 respectively.

    • Shell-model calculation of51V using pairing-plus-surface-tensor-interaction

      D Banerjee L K Chakraborty

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      Employing48Ca as the core, the structure of51V is studied in the framework of a conventional shell-model. A pairing-plus-surface-tensor-interaction is used as the effective two-body interaction. Besides all configurations arising from 1f7/2 and 2p3/2 single-particle orbits, configurations of the form$$(1f_{7/2} )^{n_1 } (1f_{5/2} )^{n_2 } $$ wheren1+n2=3 (the number of extracore protons) andn2 = 1, 2 are also considered. Low-lying energy levels are calculated and a satisfactory agreement with the experimental values is obtained. Our calculated density of states is higher than that reported previously. We also present theB(E2) values for transitions between low-lying levels and the spectroscopic factors for the50Ti (3He, d)51V reaction. The dependence of the interaction parameters on the mass number of the core nucleus is also studied.

    • Opacities of high temperature highZ plasmas

      B K Godwal S K Sikka

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      A procedure is described for computation of opacities for highZ plasmas. Bound-bound, bound-free, free-free and scattering processes are considered. The inputs for these have been obtained by solving IEEOS form of Saha’s equation. Detailed calculations of opacities have been done for tungsten and uranium up to 10 keV of temperature.

    • Kinematics of new transformations

      T M Karade

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      By constructing a composite mapping of Voigt and Lorentz transformations some new non relativistic transformations of conformal type are obtained where the laws of Maxwell’s electromagnetic theory are found to be invariant. This new scheme is consistent with some of the well established experimental facts.

    • 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.

    • Cohesion in lead chloride

      Y V G S Murti V Usha

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      The Born model is used as a method to assess the ionicity and the extent of covalent contribution to the binding in lead chloride. In the process, the Madelung constant (11·2429 with respect to cube root of unit cell volume) and cohesive energy (WL) (484 kcal/mole) are evaluated. The theoreticalWL, when compared with that derived from a thermochemical cycle indicates that PbCl2 can be considered to be ‘predominantly ionic’.

    • Diamagnetic susceptibility of some organic compounds

      N A Ahmed M A El-Kordy E El-Khooly

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      The diamagnetic susceptibilities of four aromatic compounds of known structure have been measured and the principal molecular susceptibilities have been deduced from these, knowing the molecular orientations. The anisotropy of the substituted benzene is less than that of the unsubstituted benzene. The delocalization term is greater for molecules with stronger hydrogen bonds.

    • Phase transition in potassium lithium sulphate

      T Ranga Prasad Y C Venudhar Leela Iyengar K V Krishna Rao

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      Phase transition and lattice parameter variation with temperature of potassium lithium sulphate have been studied. Precision lattice parameters have been determined at various temperatures, ranging 30°C to 400°C. The diffraction pattern obtained above 435°C differs from that taken at room temperature suggesting a structural change, contrary to the reports of Fischmeister and others.

    • The Heisenberg ferromagnet in spin coherent state representation

      B Sriram Shastry G S Agarwal I Rama Rao

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      A new approach to Heisenberg ferromagnet using the spin coherent state representation is developed. The differential operator representation of spin angular momentum operators is used to derive thec-number analogs of the basic quantum mechanical equations, viz., the Schrödinger, Bloch and Liouville equations for the Heisenberg ferromagnet. As an important illustration of our formulation, which has noad hoc assumptions and does not use any boson representation, the excitation spectrum for one, two and three spin waves is obtained. In these cases it is also shown that eigenvalue spectrum can be obtained by completely ignoring the kinematical interactions.

    • Electroluminescence in lead titanate single crystals

      D A Deshpande K R Bagree B A Patki V G Kher

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      Electroluminescence in PbTiO3 single crystals is studied with variation in applied electric field, frequency (20 Hz to 5 kHz) and temperature. The EL onset depends on the rate at which the dipole switches. Extremely sharp upward rising nature of the pulses of micro second duration suggest that there is a self maintained discharge in the dielectric due to secondaryγp mechanism. Frequency dependence of EL suggests that both the secondary mechanisms, viz. theγp andγi are active after the application of a high field and the critical field at which this occurs decreases with increase in the frequency of the applied voltage. Similarly the onset voltage decreases with increase in frequency. The temperature dependence of EL at the applied frequency of 50 Hz shows that the onset voltage is intimately connected with the coercive field of the crystal and it is minimum at the Curie point. The study suggests that EL occurs in the bulk and there is a breakdown in the dielectric due to an avalanche formation.

    • Internal equilibrium and crystal dynamics of tantalum

      O M Prakash Gupta H L Kharoo M P Hemkar

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      A lattice dynamical model for bcc metals, which satisfies the internal force equilibrium condition of the lattice is proposed. The present model combines a linearized Thomas-Fermi Theory for the electron-ion interaction and the central pair potential for ion-ion interaction. as an application, the computed phonon dispersion, vibrational spectrum, and lattice specific heat of tantalum show fairly good agreement with experiments.

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