• Volume 6, Issue 2

      February 1976,   pages  59-115

    • The deformation producing tendency of (d3/2f7/2) empirical effective interaction

      D P Ahalpara K H Bhatt

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      The effective matrix elements in (d3/2f7/2)2 configuration have been recently defined by Erskineet al. and Sherret al. assuming shell clcsures for S32 and Ca40. We have attempted to verify whether this empirically deduced (d3/2f7/2)2 interaction permits thed3/2 shell to remain closed when nucleons are added to Ca40. It is found that the Erskine interaction gives rise to ground states of thef7/2 shell nuclei in which thed3/2 orbit is completely filled. However that interaction over-binds Ca40. If the centroid of the (d3/2)2 interaction is modified to fit the Ca40 binding energy, the ground states of Cr48 and Fe52 become deformed and thed3/2 orbit is not completely filled.

    • Studies of mass and energy correlations in thermal neutron fission of U-235 accompanied by long range alpha particles

      R K Choudhury S S Kapoor D M Nadkarni P N Rama Rao S R Srinivas Murthy

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      Several characteristics of fission accompanied by long range alpha particles (LRA) have been studied in the thermal neutron induced fission of235U. The kinetic energies of fission fragments and the LRA were measured with a back-to-back ionization chamber and semiconductor detectors respectively. The kinetic energies of the two fragments and the LRA in LRA fission, along with the energies of pair fragments in the normal binary fissions, were recorded event by event on a magnetic tape by means of a four-parameter data acquisition system. The data were analysed to study the dependence of different quantities in LRA fission on the fragment mass ratio, LRA energy and the total kinetic energy of the fission fragments. It is seen that the most probable energy of LRA increases significantly for near symmetric mass divisions. The total kinetic energy for all mass ratios in LRA fission is found to be (2.6±0.7) MeV larger than that in binary fission. The difference in the total kinetic energies in LRA and binary fissions is seen to be dependent on mass ratio. This result may suggest that the scission configuration in LRA fission is different for different mass ratios. Correlations between the fission fragment and LRA energies have been studied for several mass ratios. It is seen that the most probable fragment kinetic energyĒk varies nearly linearly with the LRA energyEa for various mass divisions but the variation of the most probable LRA energyĒa with fragment kinetic energyEk is found to deviate from linearity for several mass ratios. From a least square fit to the variation ofĒk withEa it is found that the slope (k/dEa) increases with the increase in mass ratio. The present results are discussed to arrive at a better understanding of the scission configuration in the fission accompanied by LRA emission.

    • Stability of magnetopause boundary and generation of long period geomagnetic pulsations

      S P Mishra K D Misra R N Singh

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      The effect of irrotational electric field and tensorial plasma conductivity on the growth rate of Kelvin-Helmholtz instability has been investigated. It is shown that the presence of irrotational electric field alters the growth rate. The dependence of Pedersen conductivity on the growth rate has been shown. The Kelvin-Helmholtz perturbations generate a surface wave in the frozen-in plasma. The propagation of these waves gives rise to polarization of the transverse hydromagnetic pulsations. It is shown that the modified K-H spectrum would result in a corresponding change in polarization features of the hydromagnetic pulsations.

    • Equation of state and temperature variation of the bulk modulus of the alkaline earth fluorides

      R Srinivasan V Ramachandran

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      The isotherms for the alkaline earth fluorides (CaF2, SrF2 and BaF2) have been computed using the expression for the total free energy of a crystal in the quasiharmonic approximation. The theoretical points for SrF2 and BaF2 have been compared with the points derived from Bridgman’s experimental relation.

      The temperature variation of the isothermal bulk modulus of the alkaline earth fluorides has been worked out on the basis of Axe’s shell model. The theoretica points are compared with the points obtained from the temperature variation of the elastic constants data. It is found that the vibrational contribution to the temperature variation of the elastic constants in these crystals is significant.

    • Neutron diffraction study of ammonium tartrate (NH4)2C4H4O6

      V S Yadava V M Padmanabhan

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      A neutron diffraction study of ammonium tartrate has been carried out. Using the diffractometer in symmetrical setting, intensities of 750 reflections have been measured. The positions of all the hydrogen atoms have been determined. A good agreement is noticed between the present neutron and the earlier x-ray heavy atom parameters. The tartrate ion consists of two nearly identical planar halves, with an interplanar angle of 62°. Tre structure is stabilized by a net-work of hydrogen bonds. Details of hydrogen bonding and the ammonium ions environment are discussed.

    • Effect of ion implantation on the refractive index of glass

      P K Bhattacharya N Sarma A G Wagh

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      Studies on the changes of the index of refraction in glass due to ion implantation provide an insight into the structure of amorphous substances, besides being important for the development of techniques for the production of optical integrated circuits. Using a heavy ion accelerator, optically flat samples of Pyrex and Corning borosilicate glass were implanted with ions of gallium and argon at various incident energies and doses. The refractive index was then measured and found to be between 1.5 and 1.8 at a wavelength of 5893 A.U. The change in the refractive index was found to vary linearly with the incident dose irrespective of the ion species. This suggests that bombardment damage is mainly responsible for the effect. The dependence of the refractive index change on the incident dose however depends strongly on the chemical composition of the substrate glass.

    • Images of an incoherent annulus in the presence of transverse sinusoidal vibrations

      K Singh R Rattan

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      The diffraction image of an incoherent bright annular test object is obtained by using Fourier transform method. The effect of transverse sinusoidal vibrations has been studied and results are given in graphical form for various sizes of the object. It is observed that in certain cases the presence of vibrations completely distorts the object. Hence a detailed analysis of image intensity distribution should prove useful in aerial reconnaissance work and performance evaluation tests.

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