Volume 28, Issue 6
June 1987, pages 1-697
pp 1- June 1987 Rapid Communications
The results of x-ray diffraction, electrical resistance, DC and AC magnetization studies on two specimens of compositions Y2.1Ba3.9Cu6O14−δ and Y1.8Ba4.2Cu6O14−δ are presented. Our studies confirm that La3Ba3Cu6O14 type orthorhombic phase is responsible for superconductivity in the 90 K range. The heat treatment that yields high quality samples with sharp transition in electrical resistance as well as in AC magnetic susceptibility measurements is described. Magnetic response just belowTc is found to be sensitive to the measuring field.
pp 607-616 June 1987 Particle Physics
Using fits to the available data on the pion and deuteron electromagnetic form factors and the Chou-Yang model, the computed values of differential cross-sections for high-energy pion-deuteron elastic scattering agree reasonably well with the available experimental data. Whereas only a shoulder is expected to appear up to energies of several hundreds of GeV, a dip and a secondary maximum are predicted to be conspicuous only forPlab≫400 GeV/C. The position of the dip starts at a much lower value, |td| ≅ 0.5–0.6 GeV2, as compared to the corresponding position in thepp scattering. The positions of the first dip are plotted against total cross-section which can be verified by future high-energy experiments. Limitations of the model predictions for ultrahigh energies are pointed out.
pp 617-619 June 1987 Particle Physics
Using the Ward-Takahashi identities from the hidden supersymmetry in Langevin equation we present a very simple proof of the equivalence of stochastic quantization to field theories.
pp 621-632 June 1987 Particle Physics
A supersymmetric version of the left right symmetric partial unification group SUC(4) × SUL(2) × SUR(2) is presented. The spontaneous breakdown of gauge symmetry in a favourable chain of descent has been studied in detail. The mass spectra have been calculated. The method of O’Raifeartaigh has been used to break supersymmetry. The lifting of degeneracy of mass levels between physical multiplets has been shown to occur due to radiative corrections.
pp 633-639 June 1987 Particle Physics
Using the configuration-space HamiltonianH+ which is derivable within the framework of quantum electrodynamics, we extend the Hohenberg-Kohn theorem to the relativistic theory of electrons in atoms or molecules.
pp 641-644 June 1987 Nuclear Physics
A shell model description of heavy nuclei is used to show that the density of nucleons in heavy nuclei is of the formρ(r) =K(a2 −r2)3/2,K, a being constants. Two broad features of this distribution are mentioned.
pp 645-651 June 1987 Nuclear Physics
An elegant and fast method for the calculation of geometrical structure coefficients needed for an expansion of a few-body wavefunction and interaction in hyperspherical harmonics has been proposed. A sum rule for the GSC has also been derived, which is useful for an independent check of the coefficients. The proposed method of computation is many orders of magnitude faster than conventional methods.
pp 653-660 June 1987 Molecular Physics
The rate of quenching of excitons in a one-dimensional molecular crystal by an impurity is quantum-mechanically calculated.
pp 661-667 June 1987 Optics
The applicability of Kramers-Kronig (K-K) relation under nearly sharp resonant transition regime in narrow-gap semiconductors has been established and consequently, a generalized dispersion relation for nonlinear optical susceptibility of a dielectric is derived. This relation can be employed in the study of nonlinear optical processes in solids as well as in plasmas over a wide frequency spectrum.
pp 669-673 June 1987 Condensed Matter Physics
A simple relation for calculating the electronic contribution to the electric field gradient in dilute alloys of transition metals is reported and is compared with the conduction electron charge shift model. The dependence of the field gradient on thes andd electrons and the difference in radii between the host and the probe atoms is considered for calculating the field gradient. It is found that thed electrons are the major contributors to the field gradient.
pp 675-688 June 1987 Condensed Matter Physics
X-ray, electrical conductivity, magnetic hysteresis and IR studies for the system Co2−xGe1−xFe2xO4 were carried out. All the compounds, 0⩽x⩽1, showed cubic symmetry. X-ray intensity calculations, magnetic hysteresis measurements and IR studies indicated the presence of Ge4+ at tetrahedral, Co2+ at octahedral and Fe3+ at both the sites. The activation energy and threshold frequency decreased with increasing value ofx. The compounds withx⩽0.5 arep-type and those withx⩾0.75 aren-type semiconductors. Magnetic hysteresis indicated that all the compounds are ferrimagnetic except forx=0 which is antiferromagnetic. The shapes of χ/χi vsT plots, highHc values andJR/Js ratios showed that all the compounds exceptx=0 exhibit single-domain behaviour. Curie temperature,Tc increased with increasing Fe3+ ions. The probable ionic configuration for the system is suggested as Ge1−x4+Fex3+ [co2−x2+ Fex3+]O42−.
pp 689-697 June 1987 Condensed Matter Physics
A comprehensive unified study of fcc alkaline earth metal Ca, Sr and the bcc phase of Sr and Ba has been made. Properties studied include equilibrium lattice parameter, total crystal energy, second order elastic constants, pressure derivative of the second order elastic constants and phonon spectrum in the symmetry direction. The results obtained show an overall agreement with experiment. The results partially reproduced the experimentally observed phonon-crossover in Ba, and this has been found as the many-body effect in lattice dynamics.
Volume 93 | Issue 5
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