• Volume 31, Issue 5

November 1988,   pages  1-420

• The structural-chemical state of57Fe in high-temperature superconductor YBa2Cu3O7−δ

Mössbauer spectra using ion-57 and tin-119 nucleii in YBa2Cu3O7−δ oxides are reported, using samples prepared under different conditions of heat and gas treatment. The separation of copper charge states between different structural positions is supported by these studies.

• Certain class of generalized isotropic perturbations of thes-wave three-dimensional harmonic oscillator

In this paper we study a certain class of generalized perturbation problem for the isotropic three dimensional harmonic oscillator, forl=0 states only, for all excited states. The efficacy of our formalism is tested by studying the Killingbeck potential in detail. We also briefly present our results using the diagonal Padé approximants.

• Triple differential cross-sections for the fast electron/positron impact ionization of hydrogen and helium in the Glauber approximation

Triple differential cross-section for electron and positron impact ionization of hydrogen and helium are calculated by using the Glauber approximation along with post-collision interaction effects which are estimated classically. The present results are compared with the recent absolute data of Ehrhardt, Jung and coworkers for the electron impact case. The positron impact case is found to lead to a larger binary to recoil peak maxima ratio (compared to the electron impact case) which further increases when post-collision interaction effects are included.

• Some aspects of laser-metal vapour interaction

The vapour beam interaction plays an important role in laser machining process, since the vapour generated on the workpiece surface absorbs some fraction of the incident beam and heats the workpiece surface. Consequently, a study of this interaction mechanism is essential. For this purpose, a computer program was developed to investigate the interaction interaction, it provides a foundation to do further studies. It was found that the vapour locally high pressure gradients. Although the analysis presents a simplified picture of the interaction, it provides a foundation to do further studies. It was found that the vapour temperature reaches 5000 K after 10−6 s for a laser pulse of 1011 W/m2 power intensity. The leading edge of the vapour velocity had a velocity of the order of 4000–7000 m/s.

• Γ andX bandgap hydrostatic deformation potentials for epitaxial In0.52Al0.48As on InP(001)

The pressure dependence of the direct and indirect bandgap of epitaxial In0.52Al0.48As on InP(001) substrate has been measured using photoluminescence up to 92 kbar hydrostatic pressure. The bandgap changes from Γ toX at an applied pressure of ∼ 43 kbar. Hydrostatic deformation potentials for both the Γ andX bandgaps are deduced, after correcting for the elastic constant (bulk modulus) mismatch between the epilayer and the substrate. For the epilayer we obtain$$(\Xi _d + \tfrac{1}{3}\Xi _u - a) as - (6 \cdot 92 + 0 \cdot 3) eV$$ and+(2.81±0.15)eV for the Γ andX bandgaps respectively. From the pressure dependence of the normalized Γ-bandgap photoluminescence intensity a Γ-X lifetime ratio, (τΓX), of 4.1×10−3 is deduced.

• Effect of iron doping and oxygen stoichiometry on infrared absorption in Y1Ba2Cu3O7−δ

We report infrared absorption of Y1Ba2Cu3O7−δ as a function of oxygen stoichiometry (0&lt;δ&lt;1) and copper substitution by iron in the spectral range of 450–700 cm−1. The strong bands associated with Cu-O vibrations undergo significant changes in their frequencies and intensities asδ is varied across the orthorhombic to tetragonal phase. These changes coupled with those arising as a result of doping with iron has helped in identifying the nature of the vibrational modes.

• Computer simulation of proton channelling in beryllium

The channelling of protons through a thin beryllium crystal is simulated in a computer. The angular dependence of the momentum density is computed using particle trajectory approximation and is reported as the transmission spectra. In obtaining the spectra, the energy loss suffered by protons due to electron multiple scattering is considered and the effect of thermal vibrations treated separately. The spectra obtained are characteristic of the hcp structure of Be. Positions of the major dips in the transmission spectra are found to correlate well with the directions of neighbouring strings. Variations in the angle of incidence of the beam and in its initial azimuthal angle bring about modifications in the spectra depending on the transverse kinetic energy of the incident particles and the crystalline structure of Be. Thermal vibration of the lattice does not modify the spectra appreciably.

• Charge storage and relaxation process of polymer film by thermally stimulated discharge current technique

Charge storage and relaxation process of the polymide film electret were investigated using the thermally stimulated discharge current technique. Homo- and heterocharges were mainly observed up to and above the polarization temperature.

• # Pramana – Journal of Physics

Volume 94, 2019
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019