Phase formation in Fe0-H2O-O2 system in the presence of iron cations: 1. Fe0-H2O-O2-FeSO4 system

Formation mechanisms of ultradispersed (nanosized) iron-oxygen particles in a Fe⁰-H₂O-O₂ system in the presence of bivalent iron cations are investigated. It is shown that, depending on the solution concentration and pH and the presence or absence of an oxidant, nanosized nucleation structures, mainly protolepidocrocites, are formed on the surface of an iron sample, in a surface layer of the sample, and in the solution. Subsequent development of these structures proceeds through several mechanisms to yield ultradispersed phases of iron oxides and monohydrates with different crystalline structures.     

Subwavelength Hyperlens Resolution With Perfect Contrast Function

Recently it has been shown that plasmonic effects in hyperbolic metamaterials may facilitate overcoming the diffraction limit and enhance the contrast function of an image by filtering background radiation. Unfortunately, the contrast function of such a dark‐field hyperlens degrades in the deep‐subwavelength regime. We push forward the concept of the contrast function revival in the subwavelength imaging by introduction of the proper phase difference between coherent sources. To study this effect we develop a simplified theory of the wave propagation through a hyperbolic metamaterial and show that, in principle, two sources standing apart at any subwavelength distance can be distinguished. We suggest two feasible designs, the first of which employs the obliquely incident light, while the second one is based on a properly designed metasurface. The concept can be used in high‐contrast subwavelength microscopy.     

Metamaterial polarization converter analysis: limits of performance

In this paper, we analyze the theoretical limits of a metamaterial-based converter with orthogonal linear eigenpolarizations that allow linear-to-elliptical polarization transformation with any desired ellipticity and ellipse orientation. We employ the transmission line approach providing a needed level of the design generalization. Our analysis reveals that the maximal conversion efficiency for transmission through a single metamaterial layer is 50 %, while the realistic reflection configuration can give the conversion efficiency up to 90 %. We show that a double layer transmission converter and a single layer with a ground plane can have 100 % polarization conversion efficiency. We tested our conclusions numerically reaching the designated limits of efficiency using a simple metamaterial design. Our general analysis provides useful guidelines for the metamaterial polarization converter design for virtually any frequency range of the electromagnetic waves.     

Secondary radiation in the x-ray fluorescence analysis of samples with arbitrary composition

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 6, pp. 928–934, December, 1991.     

Two-quantum transitions between the fine-structure levels of a hydrogen-like atom

A study is made of the probability of two-quantum spontaneous transitions between fine-structure levels for fixed value of the principal quantum number (the radiation spectrum and the total transition probabilities are calculated) on the basis of the solution of the Dirac equation in a Coulomb field with arbitrary value of the charge of the nucleus.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 20–24, July, 1980.     

Electron photoemission in plasmonic nanoparticle arrays: analysis of collective resonances and embedding effects

We theoretically study the characteristics of photoelectron emission in plasmonic nanoparticle arrays. Nanoparticles are partially embedded in a semiconductor, forming Schottky barriers at metal/semiconductor interfaces through which photoelectrons can tunnel from the nanoparticle into the semiconductor; photodetection in the infrared range, where photon energies are below the semiconductor band gap (insufficient for band-to-band absorption in semiconductor), is therefore possible. The nanoparticles are arranged in a sparse rectangular lattice so that the wavelength of the lattice-induced Rayleigh anomalies can overlap the wavelength of the localized surface plasmon resonance of the individual particles, bringing about collective effects from the nanoparticle array. Using full-wave numerical simulations, we analyze the effects of lattice constant, embedding depth, and refractive index step between the semiconductor layer and an adjacent transparent conductive oxide layer. We show that the presence of refractive index mismatch between media surrounding the nanoparticles disrupts the formation of a narrow absorption peak associated with the Rayleigh anomaly, so the role of collective lattice effects in the formation of plasmonic resonance is diminished. We also show that 5–20 times increase of photoemission can be achieved on embedding of nanoparticles without taking into account dynamics of ballistic electrons. The results obtained can be used to increase efficiency of plasmon-based photodetectors and photovoltaic devices. The results may provide clues to designing an experiment where the contributions of surface and volume photoelectric effects to the overall photocurrent would be defined.