Experimental study of a saturated multipactor in crossed fields

We propose an experimental scheme of and develop a method for studying a one-sided multipactor discharge in crossed fields in the saturation regime. Basic parameters of the discharge have been measured. In the experiment performed in a 3-cm wavelength band, the discharge develops in microwave fields with intensities from 8 kV/cm (near the lower threshold) to 20 kV/cm and became stabilized during at least a hundred cycles of multiplication of secondary electrons on the discharge surface. In this case, the maximum power absorbed in the discharge amounts up to 4 kW/cm², and the corresponding density of the saturated-discharge current, up to 10 A/cm². The measured time of discharge development is equal to 15–30 ns. These parameters agree well with estimating calculations based on approximate analytical models.     

Potassium-cationic conductivity in the mixed ferrite-aluminate solid electrolytes with five-charged cation additives

New potassium-conducting solid electrolytes in the mixed ferrite-aluminate K_1.80(Fe_{1 ? x} Al _x )_1.90V_0.10O₄ and K_1.85(Fe_{1 ? x} Al _x )_1.925P_0.075O₄ are synthesized and studied. In the first system, the conductivity only slightly depends on the composition; therefore, the composition of solid electrolyte can be optimized with respect to the conductivity-stability characteristics. In the second system, extremes and considerable negative deviations from the additivity are observed in the conductivity isotherms. Possible reasons for this phenomenon are discussed.     

Potassium-conductive solid electrolytes in systems K2 ? 2 x M2 ? x V x O4(M = Al, Fe)

New high-conductivity solid electrolytes based on potassium monoaluminate and monoferrite are synthesized by partial substitution of V⁵⁺ for three-charged cations. In both systems, the introduction of vanadium cations leads to a substantial increase in the conductivity, with the maximum values corresponding to upper boundaries of the monophase solid solution regions. The principal factors responsible for the high conductivity are the formation of potassium vacancies at the substitutions M³⁺ → V⁵⁺ + 2V’ _K and the extension of the temperature range of existence of high-temperature modifications of KAl(Fe)O₂. Original Russian Text ? E.I. Burmakin, G.V. Nechaev, B.D. Antonov, G.Sh. Shekhtman, 2008, published in Elektrokhimiya, 2008, Vol. 44, No. 10, pp. 1261–1264.     

Nature of intramolecular O→Si bond in <Emphasis Type="Italic">N</Emphasis>-(trifluorosilylmethy)succinimide and <Emphasis Type="Italic">N</Emphasis>-(trifluorosilylmethy)phthalimide

By AIM analysis with application of PBE/TZ2P(SBK-JC) method the O→Si bond in isolated molecules of N-(trifluorosilylmethyl)succinimide (I) and N-(trifluorosilylmethyl)phthalimide (II) is shown to be of donor-acceptor type. In crystalline state of compound I it also is a weak donor-acceptor bond, while in II the interaction between the oxygen and silicon atoms is of electrostatic nature.     

When are all group codes of a noncommutative group Abelian (a computational approach)?

Let G be a finite group and F be a field. Any linear code over F that is permutation equivalent to some code defined by an ideal of the group ring FG will be called a G-code. The theory of these ??abstract?? group codes was developed in 2009. A code is called Abelian if it is an A-code for some Abelian group A. Some conditions were given that all G-codes for some group G are Abelian but no examples of non-Abelian group codes were known at that time. We use a computer algebra system GAP to show that all G-codes over any field are Abelian if |G|?<?128 and |G| ? {24, 48, 54, 60, 64, 72, 96, 108, 120}, but for F?=? $ {\mathbb{F}_5} $ and G?=?S₄ there exist non-Abelian G-codes over F. It is also shown that the existence of left non-Abelian group codes for a given group depends in general on the field of coefficients, while for (two-sided) group codes the corresponding question remains open.     

Change in surface states of Ag(111) thin films upon adsorption of a monolayer of PTCDA organic molecules

The change in the electronic structure of silver thin films of different thicknesses with the Ag( 111) orientation due to the interaction with an adsorbed monolayer of ordered organic molecules of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) has been investigated in terms of density functional theory. It has been shown that one of the two surface states of the pure films transforms into an unocc upied interface state due to the interaction so that all the main features of the initial state are retained. The relation of the resulting state to the unoccupied state experimentally observed in the PTCDA/Ag( 111 ) system by scanning tunneling and two-photon photoemi ssion spectroscopy has been discussed.     

Electronic structure and excitations on clean and nanostructured metal surfaces

We present a brief overview of recent studies and new theoretical results for electron-phonon interaction in the $\overline{Y}$ surface states on FCC(110) noble metal surfaces as well as in surface and quantum-well states of thin films. We discuss the oscillations of electron-phonon coupling parameter λ and the respective contribution to the lifetime broadening of these states. We analyse the effect of spin-orbit splitting of surface states on an electron-electron contribution to lifetimes of excited electrons (holes). Oscillations of the electron-electron contribution and quadratic dependence of the linewidth on energy is discussed for ultrathin Pb(111) films.     

Ten-Megawatt Pulsed Gyrotron with a 1-cm Wavelength and a 50% Efficiency

Development of a gyrotron driven by a relativistic electron beam and generating radiation at the wavelength 1 cm with an output power of 10 MW, an efficiency of 50%, and a pulse duration of a few hundreds of nanoseconds is reported.     

The effect of surfactant concentration on the geometry of pores resulting from etching of poly(ethylene naphthalate) films irradiated by high-energy ions

The influence of temperature and concentrations of an alkali and a surfactant in etching solutions on the structural and transport characteristics of membranes produced by etching latent tracks of high-energy heavy ions in poly(ethylene naphthalate) films has been studied. The presence of a surfactant provides the formation of spindle-shaped pores narrowing in the direction toward the film surfaces. A procedure has been developed for the quantitative assessment of the degree of widening of spindle-shaped pores in their central part. The transport properties of track membranes with spindle-shaped and cylindrical pores have been compared.     

Quantum-chemical modeling of gas-phase adsorption of the hydroxyl radical on IB metal clusters Me n (n = 2–8)

The structure of the most stable Me _n clusters and Me _n OH complexes (Me = Cu, Ag, Au; n = 2–8) was calculated using the density functional theory. The enthalpy and Gibbs energy of the interaction of OH^· with metal clusters were calculated. It was shown that the hydroxyl radical is predominantly adsorbed into the bridge position on the metal IB clusters. During the adsorption of the hydroxyl radical, the frequency and intensity of the stretching vibrations of the O-H bond increased relative to the corresponding values for the isolated state; the frequency shift changed in the series Ag < Cu < Au.