• Volume 8, Issue 2

      February 1977,   pages  99-204

    • Electron momentum distributions and compton profiles of some molecules with FSGO model

      S R Gadre R Ramaswamy P T Narasimhan

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      The electron momentum distributions and the Compton profiles (within the impulse approximation) of H2, LiH, methane, water, acetylene, ethylene, ethane cyclopropane and cyclobutane have been calculated using the floating spherical Gaussian orbital (FSGO) wavefunctions. The agreement of the single-FSGO Compton profiles with the corresponding experimental or the Hartree-Fock (HF-SCF) theoretical ones is fairly good in most of the cases examined. The advantages and drawbacks of using the FSGO model for the calculation of Compton profiles are discussed.

    • On the potential energy curves of LaO molecule

      S H Behere P L Sardesai

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      Turning points for several electronic states of LaO molecule are calculated using the Rapid method by Morse function, and compared with those obtained by RKR method. The electronegativity potential function and RKR potential functions are compared for the ground state of the molecule and an estimate of dissociation energy of LaO molecule in the ground state is reported.

    • An approximation method for evaluating centrifugal distortion constants in XY2 bent symmetric nonhydride molecules

      T R Ananthakrishnan C P Girijavallabhan

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      An approximation method is preser ted for an easier evaluation of centrifugal distortion constants ταβγδ in XY2 bent symmetric ronhydride molecules, employing the known extremal properties of the intramolecular force constants. The formulas for ταβγδ thus obtained involve only atomic masses, geometry and normal vibrational frequencies of the molecule. The centrifugal distortion constants calculated under this approximation compare very well with experimental values obtained from the microwave spectrum.

    • An electron fluid model for the lattice dynamics of metals

      S K Das D Roy S Sengupta

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      An electron fluid model is proposed for the lattice dynamics of metals which satisfies the requirement of translational invariance and the lattice is in equilibrium without recourse to external forces. The model is applied to calculate the phonon dispersion of sodium in the symmetry directions.

    • Dispersion and spectral characteristics of crossfield instability in collisional magnetoplasma

      Y C Saxena P I John

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      Results on dispersion and spectral characteristics of crossfield instability in a collisional magnetoplasma are presented for different values of externally applied radial electric field. The dispersion relation obtained experimentally differs significantly from predictions of linear theory for strong electric fields.K-spectra for density and potential fluctuations follow power law with indices (−3·7 ± 0·5) and (−5·6 ± 0·6) respectively.

      At large values of applied electric fields, the main crossfield modes appear to give rise to a number of other modes possibly through non-linear wave-wave interactions. Large amplitudem = 2 mode displays strong sidebands indicating particle trapping by the non-linear waves. Non-linear wave-wave and wave particle interactions, thus, appear to play at important role in the saturation of the cross field instability.

    • Tachyon emission from white-holes

      S V Dhurandhar

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      Investigations are made about the motion of a radially outward propagating tachyon which is created in the singularity with the white-hole. The problem of confinement or escape of such a tachyon from a white-hole is discussed. It is shown that the confinement or escape of the tachyon depends on the maximum radius of the white-hole and also on a parameterk (defined in the text) associated with the momentum of the tachyon. Also it is shown that when a tachyon escapes it always escapes beofre the white-hole has expanded to half its Schwarzschild radius.

    • Alpha-preformation in even-even alpha emitters: An alpha-decay without tunnelling approach

      M K Basu

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      An ‘alpha-decay without tunnelling’ approach shows that alpha-preformation probability in trans-lead even-even alpha-emitters lies in the range of 0·17–0·08, indicating a clear shell-closure effect atN = 126 and exhibits appreciably enhanced values in open-shell nuclei and executes a zig-zag nature with increasing neutron number in an isotopic series. All these findings are in fair qualitative agreement with experimental observations. Experimental results are found to overestimate this parameter for these heavy deformed nuclei.

    • Elastic and the 2+ inelastic scattering of high energy protons on12C and the alpha-particle model

      Z A Khan I Ahmad

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      The alpha-particle model has been applied to calculate the elastic and the 2+ inelastic angular distribution of 1 GeV protons on12C within the framework of Glauber multiple scattering theory. The results are compared with the recent experimental data and with some previous calculations. The model gives a fairly good account of the inelastic data and its predictions for the elastic scattering are essentially the same as those of the shell model.

    • Improved unitarity bounds for inclusive reactions of particles with spin

      P P Divakaran A S Vengurlekar

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      A comprehensive discussion of the unitarity bounds on inclusive angular distributions, given the elastic amplitudes and the integrated inelastic cross section, is presented. The role played by the latter constraint in improving the bound is studied in detail. Calculations are made forπ±pp (inclusive) at 6 GeV/c.

    • Neutral current effects in the parity violating nuclear force

      K Datta V K Gupta N Panchapakesan J N Passi R P Saxena

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      The measurements of the ΔI = 1 part of the parity violating nuclear force when combined with information on neutral current couplings from neutrino scattering and pion production experiments allow an estimate of the isoscalar admixture in the neutral current if it has a vector axial-vector structure has been shown.

    • A simple white beam neutron diffraction technique

      A H Venkatesh K R Rao

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      White beam neutron diffraction by time-of-flight (TOF) technique has been studied over a number of years as it is believed to be the most convenient method to investigate solids in a fixed geometry. This technique needs a pulsed neutron source and a suitable multichannel, analysing system. The entire system is in general, mechanically quite intricate and expensive.

      We have investigated an alternative technique to achieve the end result of a constant geometry around the diffracting sample. This involves the use of a single crystal as an analyser to study diffraction pattern from the sample bathed in a white beam and diffracting at any fixed scattering angle. In this paper we report the results of our investigations and have compared this technique with other diffraction techniques. Taking Si, KCl and KNO3 as typical specimens we have illus. trated the results of our technique and we find that the results are comparable to those obtained by conventional neutron diffraction and TOF diffraction. The technique is simple in mechanical design and data acquisition. It can be easily adapted for high pressure diffraction which is being attempted.

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