• Volume 2, Issue 4

      April 1974,   pages  171-228

    • Thermoelectric power of cerium at high pressures

      T G Ramesh A S Reshamwala S Ramaseshan

      More Details Abstract Fulltext PDF

      The electronic phase transition in cerium occurring near 7 kbar pressure at room temperature which is attributed to the 4f–5d electron promotion has been studied using thermoelectric power as a tool. The important results that have emerged out of this work are: (a) the relatively large variation in the absolute thermoelectric power ofγ-cerium (normal fcc phase) with pressure prior to the phase transition (in contrast to the rather small resistivity change with pressure in this region); (b) a sharp decrease in the thermoelectric power accompanying the iso-structuralγ-α phase transition; and (c) the continuous decrease in the thermoelectric power ofα-cerium (collapsed fcc phase) with pressure, ultimately changing sign at higher pressures. An explanation based on the “virtual bound state” model is proposed to account for these results.

    • Lattice dynamics of beryllium

      B A Dasannacharya P K Iyengar R V Nandedkar K R Rao A P Roy C L Thaper

      More Details Abstract Fulltext PDF

      Phonon frequencies in beryllium along the principal symmetry directions have been determined by means of the slow neutron inelastic scattering technique. The data are analysed in terms of a six-neighbour force constant model and the force constants are evaluated. It is concluded that strong tensor forces are present in beryllium and the importance of this finding to basic theories of lattice dynamics is pointed out.

    • An electron in the field of phonons and magnons

      S S Shah K P Sinha

      More Details Abstract Fulltext PDF

      The behaviour of a conduction electron in the presence of two Bose fields, namely, phonons and magnons in ferromagnetic semiconductors is studied. The effects of both electron-magnon and electron-phonon interactions on the energy renormalization are calculated.

    • Sizes and electronic polarizabilities of divalent ions in crystals

      S D Bisarya Jai Shanker

      More Details Abstract Fulltext PDF

      The Pauling’s form for the overlap repulsive energy is used to calculate the sizes of isoelectronic divalent ions in MgO, CaS, SrSe and BaTe crystals by minimising the next nearest neighbour repulsive interaction. The radii calculated by this method differ significantly from the conventional sets of ionic radii in a consistent way, being larger for cations and smaller for anions. The polarizability-radius cube relation is also utilized to calculate the electronic polarizabilities of ions. The electronic polarizabilities, thus obtained agree with the values determined from the refractivity measurements.

    • Structure calculations in18O nucleus

      J N De M K Pal

      More Details Abstract Fulltext PDF

      A multishell Hartree-Fock calculation for18O nucleus has been done with the Tabakin and Hamada-Johnston interactions followed by pairing correlations and angular momentum projection. TheB(E2) transition rates have been reproduced with an effective charge of 1.5e for protons and 0.5e for neutrons, but the fit to energy levels is poor. An approximate alternative formalism has then been developed which casts the eighteen-particle problem into a two-valence nucleon problem. The two valence nucleons interact through the RPA-type oscillation modes of the core. Calculations with the two interactions mentioned above have reproduced roughly the uncorrelated projected Hartree-Fock spectrum. Lastly, the excited band spectra of18O have been examined in the TDA approach followed by band mixing.

    • Microwave spectrum and dipole moment of pentafluorobenzene

      S Doraiswamy S D Sharma

      More Details Abstract Fulltext PDF

      With the idea of evaluating the dipole moment of pentafluorobenzene from a lowJ transition, its microwave spectrum was investigated in the frequency region of 8,000 to 12,400 MHz. The spectrum had been earlier observed by the authors in the 12,400 to 18,000 MHz region which needs reassignment in the light of present investigations. The rotational constants areA=1480·856±0·003 MHz,B=1030·066±0·003 MHz andC=607·496±0·002 MHz. The dipole moment is 1·44±0·05 D.

    • Analysis of the neutral-current interaction in the inclusive neutrino reaction

      G Rajasekaran K V L Sarma

      More Details Fulltext PDF
    • Crystal shape effect on nuclear orientation thermometry at ultra-low temperatures

      T S Radhakrishnan Girish Chandra

      More Details Abstract Fulltext PDF

      Absolute temperature measurement (T < 100 mK region) from anisotropy of gamma radiations emitted from oriented60Co nuclei in a single crystal of hcp cobalt is found to depend on the shape of the crystal. This dependence is attributed to some closure magnetic domains not oriented along thec-axis of the disc shaped crystal studied. A long rectangular strip of cobalt crystal is found to give correct angular distribution ofγ-radiations and, therefore, suitable for thermometry.

  • Pramana – Journal of Physics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.