Vibrational spectra and structure of caprolactamates of group II metals

Differences between the IR and Raman spectra of the dicaprolactamates of Mg, Ca, and Ba indicate differences in their structures. Barium dicaprolactamate has an ionic structure, while the dicaprolactamates of Mg and Ca are partially covalent and have one-dimensional chain structures with various types of NCO group (terminal, bridge). In solution the dicaprolactamates of Mg and Ca are associated on account of the formation of bridged NCO groups. It was shown that the vibration frequencies of the bridged NCO groups lie in the range 1580–1620 cm^–1, and those of the terminal groups in the range 1550–1580 cm^–1.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1570–1573, July, 1990.     

The Balescu-Lenard collision term for a quark plasma. Classical model

The collision term for a classical model of a quark plasma is found. By truncation of the color hierarchy, an approximation for the collision term in a quantum model without allowance for spin is obtained.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 103, No. 1, pp. 123–137, April, 1995.     

Hyperfine magnetic anomaly in the atomic spectra of rare-earth elements

Hyperfine-splitting constants in the optical spectra of rare-earth elements, Nd, Eu, Gd, and Lu, were measured using the laser-induced resonance fluorescence in a low-divergence atomic beam. Values of the hyperfine magnetic anomaly for different atomic levels were determined by comparing the ratios of the magnetic dipole constants of neighboring isotopes with odd numbers of protons or neutrons. The relation of these values to the special features of the atomic and nuclear structure of the investigated elements is discussed.     

Structure and Thermal Stability of Nanostructured Precursor Powders of Copper(I) Sulfide and Selenide

The hydrochemical precipitation method at 298 and 333 K with, respectively, thiocarbamide and sodium selenosulfate was used to obtain nanostructured powders of copper sulfide with formula composition Cu₂S, which are composed of globules 200–500 nm in diameter, formed by 70–100-nm particles, and copper(I) selenide, composed of crystallites with polyhedral shape, sizes of 80 to 500 nm, and a formula composition Cu_1.84Se. An X-ray diffraction analysis revealed the orthorhombic Cu₂S structure (space group no. 39-Abm2) with unit cell parameters a = 1.182 nm, b = 2.705 nm, and c = 1.343 nm. Powders of Cu_1.84Se copper selenide have a cubic structure (space group Fm3m) with lattice constant a = 0.5693 nm. A thermal analysis demonstrated that the chemically precipitated Cu₂S and Cu_1.84Se powders have a stable elemental composition up to 200–240°C. An intense oxidation of the samples begins at a temperature exceeding 250°C and is accompanied by a sharp decrease in their content of sulfur (selenium) and by an increase in the content of oxygen.     

Unusual sandwich platinum(II) complex: [Pt(phen)2]2+ cation between two Pt(phen)(OOCMe)2 molecules

New carboxylate platinum(II) complexes: syn and anti isomers of Pt(phen)(OOCMe)₂ molecular complex, [Pt(phen)(NCMe)₂](O₃SCF₃)₂, as well as unusual sandwich complex [Pt(phen)₂]²⁺ · 2syn-[Pt(phen)(OOCMe)₂] where [Pt(phen)₂]²⁺ cation is inserted between two syn-Pt(phen)(OOCMe)₂ molecules were synthesized and structurally characterized by X-ray diffraction analysis. As distinct from syn- and anti-Pt(phen)(OOCMe)₂ and [Pt(phen)(NCMe)₂](O₃SCF₃)₂ complexes with flat phenanthroline ligand, the phen ligands in [Pt(phen)₂]²⁺ cation have a curved configuration. Comparative DFT analysis of geometry of model structures phen, phen⁺, phenH⁺, and [Ptphen₂] ⁿ⁺ (n = 1, 2) showed that electron removal from phen molecule had no effect on its geometry in both free state and platinum(II) complexes.     

The reaction energies of ethylene, CO, and N2 with proton, hydrogen atom, and hydride ion

It is shown by quantum chemical simulation (MP2/aug-cc-pVTZ) that the energy of addition of H⁺, H^·, and H^? decreases in the order ethylene, CO, and N₂. The energies of additions of CF₄, dimethyl ether, and BF₃ to the ions and radicals formed were calculated. Unlike the CH₃CH₂ ^? ion, the HCO^? ion can add exothermically not one, but two BF₃ molecules.     

1-THz low-noise SIS mixer with a double-dipole antenna

A quasi-optical mixer containing two Nb/Al/AlO_x/Nb superconducting tunnel junctions integrated into a NbTiN/SiO₂/Al microstrip line is studied experimentally in the 800–1000 GHz frequency range. The mixer is developed as an optional front end of the heterodyne receiver operating in frequency band 3 or 4 and incorporated into the HIFI module of the Herschel space-borne telescope. The double-dipole antenna of the mixer is made of NbTiN and Al films; the quarter-wavelength reflector, of a Nb film. The mixer is optimized for the IF band of 4–8 GHz. The double-sideband noise temperature T _RX measured at 935 GHz is 250 K at a mixer temperature of 2 K and an IF of 1.5 GHz. Within 850–1000 GHz, T _RX remains below 350 K. The antenna pattern is symmetrical with a sidelobe level below −16 dB.     

Polarization modulation of light in an optical waveguide under lateral compression

It is shown that a lateral pressure applied to a circular single-mode optical waveguide changes the phase difference between two orthogonally polarized modes and thereby modulates the polarization state of light (elastooptic effect). The efficiency of polarization modulation is characterized by a strain-to-phase difference conversion factor as applied to polarization modes of the fiber. An expression relating the phase difference between the modes and the displacement of squeezing plates is obtained and checked in real experiments and numerically. The efficiency of conversion of lateral pressure to phase difference between the polarization modes is shown to be fairly high, on the order of 10⁴ rad/(μm m).     

Semiclassical kinetic equations for gluons allowing for spin

A system of transport quantum equations is obtained on the basis of the gauge-covariant Wigner operator for the SU(N) gauge field. The semiclassical limit of the equations is derived. After exclusion of the mean field, the kinetic equations describing nonvirtual (thermal) gluons accounting for spin are separated from the system in the collisionless approximation. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 111, No. 2, pp. 263–278, May, 1997.