Investigation of invisible oscillation on the photodetachment cross-section of H_{2}^{-} near a hard surface

Induced effects in the photodetached electron spectra from a diatomic negative ion (H $_2^-$ ) near a hard surface are investigated. A z-polarized laser is used to knock off electrons from H $_2^-$ in the vicinity of a hard surface. Theoretical imaging method is used to derive a generalized modulation function for the total photodetachment cross-section, which describes invisible oscillation. It is found that the hard surface strongly affects the detached electron flux as well as total photodetachment cross-section. There exists strong dependence on the distance of H $_{2}^{-}$ from the hard surface and also on the separation of atomic centres of H $_2^-$ . Unlike the detached electron flux, no visible oscillations are noted in the photodetachment cross-section.     

Ambipolar Diffusion in Direct-Current Positive Column with Variations in Radius of Discharge Tube

The ambipolar diffusion and argon ion mobility as functions of the reduced electric field and pressure times the tube radius are investigated in a weakly ionized non-uniform glow discharge plasma system. In particular, the variable cross section at the same discharge tube on the ambipolar diffusion coefficient shows a more noticeable effect than the effects from the ion mobility. As the diffusion length A increases, the ambipolar diffusion Da increases. However, it decreases as the discharge current is increased.     

Physical hydrodynamic propulsion model study on creeping viscous flow through a ciliated porous tube

The present investigation focusses on a mathematical study of creeping viscous flow induced by metachronal wave propagation in a horizontal ciliated tube containing porous media. Creeping flow limitations are imposed, i.e. inertial forces are small compared to viscous forces and therefore a very low Reynolds number (Re ? 1) is taken into account. The wavelength of metachronal wave is also considered to be very large for cilia movement. The physical problem is linearized and exact solutions are developed for the differential equation problem. Mathematica software is used to compute and illustrate numerical results. The influence of slip parameter and Darcy number on velocity profile, pressure gradient and trapping of bolus are discussed with the aid of graphs. It is found that with increasing magnitude of the slip parameter, the trapped bolus inside the streamlines increases in size. The study is relevant to biological propulsion of medical micromachines in drug delivery.