• Volume 22, Issue 6

      June 1984,   pages  479-587

    • Thermodynamic and magnetic properties of the electron gas in the inhomogeneous magnetic field Hr−1

      P Achuthan K Venkatesan

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      The nonrelativistic and relativistic energy eigenvalues of the electron in the inhomogeneous magnetic fieldHz=Hr−1,r=(x2 +y2)1/2 are derived in a form displaying the explicit spin dependence. The possibility of magnetic hydrogen atom formation and the spontaneouse+e pair creation following from these eigenvalues is mentioned. The expressions for pressure, energy, particle number and magnetic moment of an electron gas in this IMF are calculated in the degenerate limit. The possibility of spontaneous magnetisation,i.e., ferromagnetic behaviour, is established. Further, the pressure of the electron gas in the same type of fields is an order of magnitude higher than those in a homogeneous magnetic field and crossed homogeneous electric and magnetic fields for comparable field strengths.

    • On the quantisation of dissipative systems

      M C Valsakumar

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      Two methods of quantisation of dissipative systems are considered. It is shown that the phase space description of quantum mechanics permits computational simplification, when Kanai’s method is adopted. Since the Moyal Bracket is the same as the Poisson Bracket, for systems described by a most general explicitly time dependent quadratic Lagrangian, the phase space distribution can be obtained as the solution of the corresponding classical Langevin equations in canonical variables, irrespective of the statistical properties of the noise terms. This result remains true for arbitrary potentials too in an approximate sense. Also analysed are Dekker’s theory of quantisation, violation of uncertainty principle in that theory and the reason for the same.

    • Deuteron form factors and the tensor force

      S S Mehdi V K Gupta

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      Results of a non-relativistic calculation of deuteron form factors are presented for separable potentials with and without tensor force. The tensor term in triplet state is added in such a way as to keep the values of deuteron binding energy,at andr0t unaltered, so that the difference in the form factors can be regarded as the effect of tensor force only. The calculation has been performed for two different shapes of separable potentials and for three differentD-state probabilities to study their comparative effect.

    • Muon capture by16O—using a microscopic theory of particle-hole states

      V N Sridhar R Parthasarathy Y R Waghmare

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      The partial capture rates for the process,μ +16O (g·s) →16N (2, 1, 0, 3) +vμ have been calculated using the particle-hole wavefunctions obtained using self-consistent procedure. In deriving these wavefunctions, the effectiveN-N interaction has been constructed from the bare Hamada-Johnston interaction. The terms in the muon capture Hamiltonian that depend on the momentum of the capturing proton have been included and their importance in 0+ → 0 transition is exhibited. The agreement with the available experimental data is good. The need to incorporate meson exchange effects in 0+ → 0 transition is pointed out.

    • Partial structures and compressibilities of ions in fused potassium bromide

      R V Gopala Rao Sobhen Kumar Pal

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      Treating the coulomb interaction between ion species as a perturbation on the Waisman-Lebowitz solution for direct correlation function within the hard core region, the total direct correlation function in K-space has been formulated, which gives a direct method of evaluating the partial structure factors between different ion species of the fused salts through the use of Pearson-Rushbrooke equations. The partial structure factors so obtained have been applied to evaluate the partial radial distribution functions of ion pairs. In addition, many other important associated functions such as the static correlations of total number, mass and charge densities have been computed by particular linear combination of partial structure factors. The charge neutrality relate the partial structure factors to the isothermal compressibility for the wavevectorK → 0 and hence the evaluation of the compressibilities of ions in fused KBr is possible, which agrees well with the observed value. As such the present method is very useful in investigating the structure of molten salts since only the parametersσij, the distances of closest approach between ions andɛ, the effective dielectric constant (which can be estimated from the literature) are enough for this work.

    • Meson spectra with a power-law potential in the Dirac equation

      G S Sharma L K Sharma

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      A power law potential which is an equal admixture of scalar and vector parts with effective powerv ∞ 1/mq, is proposed as a quark confining potential in the Dirac equation. The model is capable of predicting the meson spectroscopy encompassing both light and heavy quark-antiquark systems in a unified way.

    • Quark potentials for mesons in the Klein-Gordon equation

      L K Sharma G S Sharma

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      Two relativistic potential models are applied to describe meson spectroscopy in a unified way, encompassing both light and heavy quark systems. A combination of linear and coulomb potentials has been investigated for Klein-Gordon equation using the WKB approximation. A power-like phenomenological potential model has also been studied in the Klein-Gordon framework. Meson masses calculated for both the potentials give a good agreement with the corresponding experimental values.

    • Reanalysis of polarised neutron data on NiRu using projection operator formalism

      R Chakravarthy L Madhav Rao

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      Projection operator formalism has been applied to analyse magnetic structure amplitudes in Ni1−xRux (x=0·027, 0·033 and 0·046) alloys. This method is suitable for metals and alloys as it does not assume any free ion form factor. A new prescription has been discussed for the local site moment and diffuse moment in this frame work. The results of the present analysis are compared with those obtained using form factor analysis.

    • Temperature dependence of dielectric constant of crystals with fluorite structure

      Lalitha Sirdeshmukh Y R Reddy

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      The experimental data on the temperature variation of dielectric constant of six crystals with fluorite structure are analysed using an approach proposed by Havinga and Bosman for ionic crystals. The temperature variation of dielectric constant is resolved in three components related to the thermal expansion, the pressure dependence of dielectric constant and the temperature variation of polarizability (theA, B, C terms). In the present work, theB term is calculated semiempirically, such that the analysis can be extended to crystals like EuF2 for which high pressure dielectric constant data are not available. For the first time, such calculations have been made for EuF2 and PbF2 at elevated temperatures. TheC term, which is related to the temperature variation ofir polarizability is seen to play a dominant role in determining the temperature variation of dielectric constant.

    • Automation of the direct current comparator resistance bridge

      R Aidun R Caton Sigurds Arajs

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      The direct current comparator resistance bridge, Model 9975, manufactured by Guildline Instruments, Inc., which permits electrical resistance measurements up to eight digits, has been fully automated. Details of this automation are described in this paper. The performance of the automated bridge is demonstrated with applications to electrical resistivity studies on some metallic alloys.

    • Frequency stability and reproducibility of iodine stabilised He-Ne laser at 633 nm

      V D Dandawate Kowsalya

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      The frequency of a 633 nm He-Ne laser is stabilised on a hyperfine-structure-component of natural iodine vapour. The third harmonic component of an applied modulation frequency is detected and a servosystem is used to lock the laser frequency to the zero-crossing of the third harmonic component. The stability and the reproducibility of the laser are determined by beat frequency experiment.

    • On the calculation of second order properties: An equation of motion approach

      M Gupta S Bhattacharyya

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      In the light of the equation of motion method a general expression for polarisability calculation has been derived. From this general expression, different approximation methods can be deduced for different choices of ground state and excitation manifold. Among these the coupled Hartree-Fock theory is the most extensively used one for polarisability calculations. It has also been shown that this theory has a simple relationship with random phase approximation.

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