• Volume 9, Issue 2

      August 1977,   pages  93-202

    • CNDO/2 calculations on the structure and properties of chlorine difluoride

      B M Deb Geeta D Mahajan V S Vasan

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      According to the open-shell CNDO/2 calculations on ClF2, performed by using the computer programme developed by Pople, Beveridge and Dobosh, the molecule is linear and stable, with equilibrium bond length 1.507Å and binding energy −173.7 kcal/mole. The molecule has a tendency to dimerise and to disproportionate into ClF3 and ClF. The netd-orbital population in the monomer is 0.88. Bonding characteristics and other molecular properties are also discussed.

    • The dirac-schwinger covariance condition in classical field theory

      K Babu Joseph M Sabir

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      A straightforward derivation of the Dirac-Schwinger covariance condition is given within the framework of classical field theory. The crucial role of the energy continuity equation in the derivation is pointed out. The origin of higher order derivatives of delta function is traced to the presence of higher order derivatives of canonical coordinates and momenta in the energy density functional.

    • Growth of yttrium iron garnet single crystals in Na2O-B2O3 flux system in air

      Tarun Bandyopadhyay Prasenjit Saha

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      Detailed studies of growth of yttrium iron garnet (YIG) in the flux system Na2O-B2O3 were made to delineate the phase stability regions of YIG and the neighbouring crystalline phases, and a tentative working diagram of Na2O-B2O3-YIG in air was drawn from the results of small batch crystal growth runs and solubility studies. The occurrence of a rather narrow field of YIG crystallization in this system was explained on the basis of relative solubilities of different oxides constituting YIG. Several long-time growth runs with some typical compositions were carried out in this system to evaluate its suitability for bulk growth of YIG crystals. The system, although possessing some inherent advantages, was found to suffer from limitations because of which the maximum size of the self-nucleated crystals grown hardly exceeded 2.00 mm.

    • Neutrino scattering on polarized deuterons

      M V N Murthy G Ramachandran K V L Sarma

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      The possible presence of anI=0 axial vector piece in the hadronic neutral current may be detected by looking for an asymmetry in the emission of the recoil deuterons in elastic scattering of neutrinos or antineutrinos on polarized deuterons. It is estimated that this asymmetry could be about 40% with the incident neutrinos in the energy range of tens of MeV.

    • Single particle SU(3) parentage coefficients

      V K B Kota

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      The single particle SU(3) parentage coefficients are calculated for the case of leading SU(3) representation in the highest orbital symmetry partition, using the method suggested by Hecht. Tabulations are given for all possible cases of identical nucleons in η=3 and η=4 shells.

    • A quark-parton description of the deep inelastic scattering processes

      R P Bajpai

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      A consistent description of various deep inelastic processes in a quark-parton model is presented. The valence quark probability distribution and the form of core quark probability distribution is fixed from the deep inelastic electroproduction data. Langacker and Suzuki prescription is used to fix thep andn quark core distribution. The differential excitation of quark currents similar to the Harari model ofe+e annihilation process is invoked in deep inelastic electroproduction and neutrino reactions. An effective phenomenological form of the weak currents associated with new quarks and the associated nucleon structure is determined.

    • α-Decay: A distinct type of spontaneous fission

      M K Basu

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      With the help of a plot of logarithmic experimental α-decay half-life of even-even α-emitters versus the fissility parameter, it is demonstrated that α-decay is a distinct type of spontaneous fission. A simple empirical relation between experimental α-decay half-life and the fissility parameter is also given. A close examination of the nature of dependence of α-decay half-life on fissility parameter reveals that Coulomb repulsive energy accelerates the process of α-decay rather than retard it.

    • Evanescent waves and the van Cittert Zernike theorem in cylindrical geometry

      G P Agrawal C L Mehta

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      The cylindrical angular spectrum of the wavefield is introduced. In this representation the field consists of homogeneous as well as evanescent waves. The representation is applied to propagation problems and an analogue of van Cittert Zernike theorem is obtained in cylindrical geometry.

    • Cerenkov radiation and its polarization

      S S Lahoti R G Takwale

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      General expression for the energy loss in Cerenkov radiation due to a charged particle possessing anomalous magnetic moment is obtained. The expressions include the spin-polarization of the particles. The contribution to the radiation due to anomalous magnetic moment is found to be small as compared to that due to charge. The interference term of charge and anomalous magnetic moment gives better contribution as compared to the term containing only anomalous magnetic moment. Polarization of the radiation as dependent on polarization of beam of particles is studied. The radiation has a dominant nature of linear polarization with small quantum corrections. The spin-flip also gives quantum correction to strong linear polarization and at threshold when phase velocity equals velocity of the particle.

    • Drift dissipative instability in a two temperature plasma

      B N Goswami Y S Satya V H Kulkarni

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      The presence of a small amount of relatively cold electrons in an otherwise hot plasma reduces the ion sound speed in the medium and hence reduces the growth rate of the drift dissipative ion acoustic mode in an inhomogeneous weakly ionized plasma. This is expected to improve the confinement time in certain magnetic confinement schemes. The propagation of a small but finite amplitude mode in the presence of ion viscosity is also investigated by using reductive perturbation method. It is shown that, when the damping due to ion viscosity is stronger than the growth due to collisions, there exists a stationary shock solution.

    • Susceptibility and magnetisation of a random ising model

      Deepak Kumar Vipin Srivastava

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      The susceptibility of a bond disordered Ising model is calculated by configurationally averaging an Ornstein-Zernike type of equation for the two spin correlation function. The equation for the correlation function is derived using a diagrammatic method due to Englert. The averaging is performed using bond CPA. The magnetisation is also calculated by averaging in a similar manner a linearised molecular field equation.

    • Group theoretical analysis of lattice vibrations in molecular crystals

      N Krishnamurthy

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      Computer programs have been developed by Warren and Worlton, for the external modes in ionic crystals where the principal axes of the radicals of groups coincide with the crystallographic axes. In this paper, we discuss the generalisation of these computer programs for molecular crystals where the principal axes do not coincide with the crystallographic axes and for molecular crystals with linear molecules having a redundant rotational degree of freedom. Our results are discussed for the q→O modes of solid NH3, N2 and CS2.

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