Analysis of applicability of translational-factor approximations to calculation of vibrational exchange rate constants in the N<Subscript>2</Subscript>–O<Subscript>2</Subscript> system under low-pressure discharge conditions

Level-to-level rate constants of single-photon vibration–translation and vibration–vibration exchange have been calculated for the N₂–O₂ system in the temperature range of 300–800 K in terms of the generalized Schwartz–Slawsky–Herzfeld theory using exact relationships and the most commonly used approximations. It has been shown that the quality of the approximation is improved with an increase in temperature and deteriorates with an increase in the vibrational quantum number. The calculated distributions of vibrationally excited species over levels for the low-pressure glow-discharge conditions substantially depend on the rate constants used in the calculation, especially in the area of high vibrational levels.     

Modeling Chemical Composition for an Atmospheric Pressure DC Discharge in Air with Water Cathode by 0-D model

This paper reports the results of the chemical composition modeling for an atmospheric pressure DC air discharge with water cathode. The modeling was based on the combined solution of Boltzmann equation for electrons, equations of vibrational kinetics for ground states of N₂, O₂, H₂O and NO molecules, equations of chemical kinetics and plasma conductivity equation. Calculations were carried out using experimental values of E/N and gas temperatures for the discharge currents range of 20–50 mA. The effect of H₂O concentration on the plasma composition was studied. The main particles of plasma were shown to be O₂(a¹Δ, b¹Σ), O(³P), NO, NO₂, HNO₃, H₂O₂ and OH. Effective vibrational temperatures of molecules were higher than gas temperature and they did not depend on the discharge current. Distribution functions on vibrational levels for N₂, O₂, H₂O and NO ground states were non-equilibrium ones.     

Change in the order parameter symmetry in the vicinity of the surface of a superconductor with <Emphasis Type="Italic">s</Emphasis><Subscript>±</Subscript> pairing

The behavior of the order parameter and the local density of states near the impenetrable surface have been theoretically studied in a two-band superconductor in which the gapless state with s _± symmetry of the superconducting order parameter is realized. It has been shown that, over a wide range of the parameters, the spatial behavior of the order parameter on the surface is not reduced to a standard suppression. If the probability of the interband reflection on the surface is of the order of or higher than the probability of the intraband reflection, it can be energetically more favorable to change the symmetry of the superconducting state near the surface from s _± symmetry to common s symmetry. The region of existence of the surface s-superconductivity is very sensitive to relative values of the interband and intraband pairing potentials. It has also been shown that the self-consistent calculation (i.e., with allowance made for the dissimilarity of the near-surface order parameter from the bulk value) can lead to a qualitatively different behavior of the near-surface local density of states as compared to the results of the non-self-consistent calculation.     

0-pi transitions in Josephson junctions with antiferromagnetic interlayers

We show that the dc Josephson current through superconductor-antiferromagnet-superconductor (S-AF-S) junctions manifests a remarkable atomic-scale dependence on the interlayer thickness. At low temperatures the junction is either a 0 or pi junction depending on whether the AF interlayer consists of an even or odd number of atomic layers. This is associated with different symmetries of the AF interlayers in the two cases. In the junction with odd AF interlayers an additional pi- 0 transition can take place as a function of temperature. This originates from the interplay of spin-split Andreev bound states. Experimental implications of these theoretical findings are discussed.     

Sign reversal of the order parameter near <Emphasis Type="Italic">s</Emphasis><Subscript>±</Subscript>-superconductor surface

The superconducting order parameter and LDOS spectra near an impenetrable surface are studied on the basis of self-consistent calculations for a two band superconductor with nodeless extended s-wave order parameter symmetry, as possibly realized in Fe-based high-temperature superconductors. It is found that for a wide range of parameters the spatial behavior of the order parameter at a surface is not reduced to a trivial suppression. If the interband scattering at a surface is of the order of the intraband one or dominates it, it can be energetically favorable to change the symmetry of the superconducting state near the surface from s _± to conventional s-wave. The range of existing of this surface conventional superconductivity is very sensitive to the relative values of interband and intraband pairing potentials. It is shown that the LDOS spectra near the surface can qualitatively differ upon calculating with and without taking into account the self-consistency of the order parameter.