• Volume 37, Issue 5

      November 1991,   pages  387-456

    • Phase-function method for Hulthén-modified separable potentials

      U Laha A K Jana T K Nandi

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      We have treated the Hulthén-modified separable potentials within the framework of the phase-function method and obtained a closed form expression fors-wave scattering phase shift. Specializing to a rank one separable potential we have found out the limiting conditions in which the Hulthén-modified phase shift goes over to its Coulomb counterpart. We demonstrate the usefulness of our approach by means of a model calculation.

    • General relativistic model for energy release of an unstable shell of charged matter in the presence of a dyon core

      C Wolf

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      We construct a formula for the energy released when a spherical shell of charged matter disperses in the presence of a dyon core. Reasons for such a dyon-charged shell configuration on a macroscopic scale stem from the recent speculation concerning the existence of CHAMPS (charged massive particles) along with the possible existence of monopoles produced around the time of nucleosynthesis.

    • The radial force on a charged particle in superimposed magnetic fields on Schwarzschild spacetime

      A R Prasanna Sai Iyer

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      Following the approach of optical reference geometry we derive the expression for the total force in the radial direction acting on a charged particle in magnetic fields superimposed on the static Schwarzschild background and show the possible existence of bound orbits for particles in the field of ultra compact objects at distancesr⩽3m wherein the Lorentz force counterbalances both the gravitational and centrifugal forces.

    • Average Λ-nucleus potentials

      Mahmood Mian

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      A few model Λ-nucleus potentials are proposed which explain the ground state binding energy data of5He and thep-shell hypernuclei satisfactorily. Potential-II is capable of distinguishing the hypernuclei of the same mass number but of differentN andZ values. The dependence of this potential on (N − Z) term indicates that there is a charge symmetry breaking component in ΛN force. Alongwith the earlier density dependent effective Λ-nucleus interaction, these potentials may be used to determine approximately the density distributions of light nuclei. From these potentials an estimate ofDΛ is also made. It is found to be in conformity with the earlier estimates.

    • A one-parameter formula for estimating the Λ well depth

      N Neelofer Mohammad Shoeb MZ Rahman Khan

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      A one parameter, semi-empirical formula for Λ-binding energy of heavy hypernuclei in the inverse powers of core mass number (Ac) has been developed in the framework of the folding model. Unlike similar calculations reported by other authors (Deloff 1971; Daskaloyanniset al 1985), we are able to take into account the effect arising from the difference in the number of protons and neutrons of the core nuclei having same mass number. The radius and diffuseness are parametrized using the experimentally known charge density data of a fairly large number of medium and heavy nuclei. The well depth parameter (i.e. Λ-binding energy in infinite nuclear matter) in the formula is obtained from a fit to theBΛ data ofΛ28Si,Λ40Ca,Λ51V andΛ39Y. Using the original Λ-nucleus potential, theBΛ of ground and the experimentally known excited states of these hypernuclei have also been calculated by solving numerically the two-body Schrödinger equation. The agreement with the experimental data is satisfactory.

    • Cross-sections of a few (n,α) and (n, p) reactions induced at 14.7 MeV neutrons

      G R Pansare P M Dighe V N Bhoraskar

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      Cross-sections of the nuclear reactions27Al(n, p)27Mg,30Si(n, α)27Mg,52Cr(n, p)52V,53Cr(n, p)53V,54Cr(n, p)54V,54Cr(n, α)51Ti and120Sn(n, α)117Cd at 14.7 Mev neutrons were measured using56Fe(n, p)56Mn and27Al(n, α)24Na as monitor reactions. For comparison, theoretical values of the cross-section for these reactions were also obtained through different approaches of compound nucleus theory and computer code Alice. Accuracies achieved in the present measured values of the cross-sections are better than those available in literature.

    • Response of triafol-TN plastic track detectors to238U-ions

      R K Jain S K Bose K K Dwivedi

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      Triafol-TN plastic detector foils have been irradiated with238U ions of energy 16.34 MeV/u and the tracks produced have been observed using the chemical etching technique. The bulk etch rate and track etch rate are determined under successive chemical etching. In our case, the validity of Arrhenius’s law is confirmed by the fact that the same value ofEa obtained for these different concentrations, within experimental errors. The results show a linear correlation between the measured track etch rate along the track and the corresponding total energy loss rate and a threshold value of ∼ 5.0 MeV/(mg/cm2) for track registration was obtained. The maximum etched track length of238U-ion in triafol-TN has been compared with the theoretically computed range.

    • Measurements of K-shell ionization cross sections of35Br,37Rb,39Y using low energy protons

      Didar Singh H R Verma C S Khurana

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      K-shell ionization cross section measurements are reported for35Br,37Rb and39Y targets caused by protons over 300–400 keV energy range in 20 keV increment. The K-shell ionization cross sections (σkl) at different energies were deduced from the Kα and Kβ X-ray production cross sections which were obtained from X-ray yields of the Kα and Kβ transitions. The experimental values are compared with the calculated values of ECPSSR theory and empirical reference cross sections. The resultant K-shell ionization cross sections are found to be in reasonable agreement with the ECPSSR theory. The Kα/Kβ intensity ratios are also presented and compared with other experimental values and also with the theoretical one-hole values given by Scofield.

    • Deformed relativistic mean field study of binding energy anomaly in neutron-rich Ne, Na, Mg nuclei

      S K Patra C R Praharaj

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      Relativistic mean field model of interacting nucleons and mesons is used to study the structure of neutron-rich Ne, Na, Mg nuclei using a deformed basis. Results for binding energies are remarkably close to experimental values, thus addressing the problem of “island of inversion” anomaly. The spins of29,31Na are correctly predicted as 3/2+.

    • Algebra for fermions with a new exclusion principle

      A K Mishra G Rajasekaran

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    • Electrical resistivity study on SmSe1−xAsx under pressure

      S Ariponnammal S Ezhilvalavan S Natarajan

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