• S K Kataria

      Articles written in Pramana – Journal of Physics

    • Scission configuration in quaternary fission

      S K Kataria

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      Trajectory calculations have been carried out to obtain information about scission configuration in quaternary fission on the basis of observed angular-correlation and energy correlations between two alpha particles in the spontaneous quaternary fission of252Cf. A number of plausible hypotheses for the scission configuration were tested against the experimental observations on the two alpha particles. The role of mutual repulsion between two alpha particles at scission in deciding the final energy angular correlations has been examined. It was found that only one hypothesis regarding scission configuration is consistent with the experimental data.

    • Nuclear level densities in self-consistent field approximation

      S K Kataria V S Ramamurthy

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      The effect of two-body nature of the nuclear shell model potential on the recent numerical calculations of the nucleai level density has been examined. For the two most widely used single particle energy level schemes based on harmonic oscillator and Woods-Saxon potential, this effect is shown to significantly modify the excitation energy dependence of the level densisties.

    • Search for superheavy elements in monazite from beach sands of South India

      S S Kapoor V S Ramamurthy M Lal S K Kataria

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      Monazite minerals obtained from beach sands of South India were examined for the presence of superheavy elements with photon-induced x-ray fluorescence method. The accumulated data of a number of runs each of several days duration do not show any convincing peaks above the background at the expected locations for superheavy elements which are above the present sensitivity of detection of about 10 ppm by weight for element 126. However, some intriguing features pertaining to structures in the x-ray spectra around 27 keV were observed, which are of interest for further investigations.

    • Classical microscopic description of particle cluster collisions: application to heavy ion collisions

      V S Ramamurthy S K Kataria

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      A classical microscopic description of the collision between two bound particle clusters, interacting via a suitable two body force is presented with a view to extend the analogy to nuclear collisions. It is shown that with a proper choice of the parameters of the two body force, the model calculations can bring out qualitatively all the essential features of low energy heavy ion collisions such as complete fusion, deep inelastic scattering and nucleon transfers. The model avoids some of the limitations of purely hydrodynamic descriptions connected with the shape parametrization, compressibility and viscosity effects, etc.

    • A new polarization potential for heavy ion fusion spin distribution

      A K Mohanty S K Kataria S V S Sastry

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      The real part of the polarization potential which depends on both energy and angular momentum is calculated in a simple way using dispersion relation. A barrier penetration model (BPM) has been used to explain the fusion cross-section and compound nucleus spin distribution for32S+64Ni system in the energy range 50–75 MeV. It is also shown that the polarization potential which only depends on energy, is not adequate to give rise to correct spin distribution even after including any radial dependence. The proposed polarization potential with implicitE andl dependences is able to explain both fusion cross-section and average spin values.

    • L-dependent heavy ion fusion potentials

      S V S Sastry A K Mohanty S K Kataria

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      The energyE and angular momentuml dependence of optical potential for fusion of16O+208Pb system, observed by Christleyet al [5], is expressed as a function of radial kinetic energy (ɛ) instead of explicitE andl dependence. It is shown that the effects of different channel couplings, which result in different effective potentials, can also be parametrized as a function ofɛ. A correlation is obtained between the energy dependent part of this effective potential and the maximum of the spin enhancement around the Coulomb barrier and both these quantities depend on the details of the channel couplings.

    • Leptodermous expansion of nuclear ground state energies and the anomaly in the nuclear curvature energy

      S K Kataria Aruna Nijasure V S Ramamurthy A K Dutta

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      The leptodermous expansion of the total ground state energy of a nucleus into volume, surface, curvature and gauss curvature contributions has been studied starting from a semi-classical energy density formalism of extended Thomas Fermi type. A numerical procedure was used to obtain the surface energy and curvature energy contributions from surface moments of energy density profilesH(r) for a sequence of nuclei withN=Z and neglecting the coulomb interaction for the three Skyrme forces. A transition to the liquid drop model type expansion in increasing powers ofA−1/3 is then made, taking into account the dependence of the central density and the surface structure on the mass of the nucleus. It is found that there is no inconsistency between the curvature contribution to the total energy in the leptodermous expansion and theA−1/3 term contribution in the liquid drop model expansion. It has been shown that the earlier apparent anomaly between the above two methods arises due to the use of semi-infinite approximation and the mass dependence of the central density and the surface structure of finite nuclei.

    • Distribution of fusion barriers

      A K Mohanty S K Kataria

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      Heavy ion fusion cross sections and compound nucleus average spin values obtained from distribution of fusion barriers are discussed. Various shapes of distribution functions are studied using a truncated Gaussian distribution function (TGD). It is shown that fusion cross section and average spin values are less sensitive to different parametrization of TGD function, whereas the second derivative of the product of energy and fusion cross sections (w.r.t. energy), obtained from the corresponding TGD functions are significantly different depending on the shape of the barrier distribution function. It is also shown byχ2 analysis of fusion cross section data that some systems favour a narrow Gaussian distribution function whereas others, for which the vibrational and rotational collective states are less important, favour a flat barrier distribution. A physical interpretation of the dynamical process that gives rise to different barrier distribution is given in the framework of microscopic coupled channel calculations.

    • A new approach for heavy ion fusion spin distribution

      S V S Sastry A K Mohanty S K Kataria

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      The method of optical model analysis of generalized elastic scattering angular distributions (GESA) has been applied to heavy ion scattering to derive fusion spin distributions. This method is used to reproduce the coupled channel fusion spin distributions. When applied to experimental data, particularly to the fissile systems like16O +232Th, the method gives large mean square spin values in agreement with “anomalous” values derived from experimental fission fragment anisotropies.

    • Effective potentials and threshold anomaly

      SVS Sastry S K Kataria

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      The strongE andL dependence of the effective elastic channel potentials is shown to be an implicit radial kinetic energy (ε) dependence. It is also shown that this effective potential satisfies the dispersion relation inε variable at the strong absorption radius. Further, the experimental data for both elastic and fusion channels are consistent with thisL-dependence of the corresponding effective potentials. The effective transfer channel potentials derived using CRC code FRESCO are shown to exhibit strong energy dependence as a result of couplings. The energy dependence of effective transfer strength for16O+208Pb and16O+232Th systems is determined using the experimental transfer angular distributions.

    • Modified WKB transmission for fusion

      S V S Sastry S K Kataria

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      In the optical model (OM) approach for fusion, absorption of flux occuring beyond the barrier position is presented in detail at low energies. It has been shown that the OM transmission can be well approximated as a sum of the WKB transmission and a long range absorption (LRA) contribution. Owing to absence of LRA, the fusion predictions of coupled channel codes based on transmission approach like the CCFUS code, do not agree with the predictions of complete coupled reaction channel (CRC) calculations based on OM approach using the code FRESCO. The CCFUS code with a modified transmission which includes LRA contribution is shown to be consistent with the CRC results using FRESCO. The static deformation of the colliding nuclei strongly influences the fusion imaginary potential and therefore the deep sub-barrier fusion cross sections.

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