Feynman diagram method for atomic collisions

Feynman diagram method of treating atomic collision problems in perturbation theory is presented and matrix elements are calculated for a number of processes. The result for the resonant charge transfer in hydrogen is identical to the well known OBK value. However, in processes like collisional ionisation, the results are different from those obtained by conventional methods.     

Anharmonic oscillator model for first order structural phase transition

Exact solutions for the motion of a classical anharmonic oscillator in the potentialV(φ)=Bφ ² ? |A|φ ⁴ +Cφ ⁶ are obtained in (1 + 1) dimensions. Instanton-like solutions in (imaginary time) which takes the particle from one maximum of the potential to the other are obtained in addition to the usual oscillatory solutions. The energy dependence of the frequencies of oscillation is discussed in detail. This can be used as a model for the first order structural phase transition in the mean field approximation. The high and low temperature behaviour of the static susceptibility is obtained. Finally, a qualitative explanation is offered for the observed central peak in ferroelectrics like SrTiO₂.     

Acousto-electric wave instability in ion-implanted semiconductor plasmas

A comprehensive investigation of excitation of acousto-electric modes and novel properties introduced due to presence of negatively charged colloids in magnetized compensated piezoelectric semiconductor plasma is presented analytically. We derive a compact dispersion relation for the acousto-electric waves in colloids laden semiconductor plasma by employing multi-fluid balance equation. It is found that the presence of charged colloids not only modifies the wave spectrum but also alters the amplification characteristics even though colloidal particles, on account of their heavy masses, do not participate in wave propagation. The results of this investigation should be useful in understanding the characteristics of longitudinal acousto-electric wave in ion-implanted piezoelectric semiconductor plasmas whose main constituents are electrons, holes and negatively charged colloids, which are stationary in the background.     

Functionalization of carbon nanotubes via nitrogen glow discharge

We have exposed single-wall carbon nanotubes (SWCNTs) to microwave-generated N2 plasma with the aim to functionalize the nanotubes. The results strongly depend on the distance between the discharge source and the sample, since nitrogen atoms generated can be lost due to recombination. No functionalization was observed when this distance was 7.0 cm. At intermediate distances (2.5 cm), the incorporation of nitrogen and oxygen onto the SWCNT was observed, while, at short distances (1 cm), products containing CN were also observed.     

Fractional Fourier analysis of defocused images

A method is proposed for a consistent analysis of defocused images using the concept of fractional Fourier transforms of Wiener, Condon and Patterson.     

Are spin-dependent forces in charmonium generated through scalar-vector admixture?

I show that if the spin-dependent confining forces are generated through scalar-vector admixture then the ³p_J splittings restrict the vector to scalar ratio to be less than half. Further it is shown that an accurate measurement of the ¹p₁ mass can clearly distinguish this model from vector and scalar exchange models.     

Radial flow of a viscous,incompressible, electrically conducting fluid between two stationary,porous discs in the presence of transverse magnetic field

The problem of incompressible, electrically conducting viscous laminar flow between two non-conducting coaxial discs is studied, in the presence of transverse magnetic field of uniform intensity, when there is constant injection or suction at the discs. The problem is interesting both mathematically and physically. The solution, for small suction or injection, has been obtained for highly viscous fluid. The velocity profiles have also been drawn graphically.     

Charge-current commutator in the framework of analytic regularization

We calculate the charge-current commutator using analytic regularization and show that it is same as that obtained by dimensional regularization on the dimensionality shell.     

Field emission theory of dislocation-sensitized photo-stimulated exo-electron emission from coloured alkali halide crystals

A new field emission theory of dislocation-sensitized photo-stimulated exo-electron emission (DSPEE) is proposed, which shows that the increase in the intensity of photo emission fromF-centres during plastic deformation is caused by the appearance of an electric field which draws excited electrons out of the deeper layer and, therefore, increases the number of electrons which reach the surface. The theory of DSPEE shows that the variation of DSPEE flux intensity should obey the following relation