Vibrational Spectra and Steric Hindrance in Trichlorophospkazoperchloroalkyl Molecules

Abstract

Recently the IR spectra of trichlorophosphazoperhaloalkyls, CI_3P[dbnd]NR_Hal, were studied,¹and the position of P[dbnd]N frequencies in the range of 1300-1500cm^?1 and those of C-N within the range of 900-1000cm^?1 were found to depend to a great extent upon the nature of the groups attached to the nitrogen atom.     

Infra-Red Spectra of the Nitrogen-15 Labelled Triphosphonitrilic Chloride

Although the vibrational spectra of triphosphonitrilic chloride, (PNCl₂)₃ (1), have been studied by numerous investigators^1–8, there is no general agreement about the frequency of completely inactive A₂ ring vibration. Besides, assignment of some overtones and combination bands is doubtful.     

Longitudinal structures in the near field of a plane wall jet

In the present study, the flow field near the orifice of a plane wall jet is in focus. Two main flow regions may be distinguished in the wall jet, i. e., a free shear layer away from the wall and a boundary layer close to the surface. In both of these layers, streamwise coherent structures are detected by means of smoke visualization and hot-wire measurements. The structures, which occur naturally, have different spanwise scales and emerge at different distance from the nozzle. Effects of the flow velocity, upstream perturbations, and acoustic excitation on the generation and characteristics of the streamwise disturbances are investigated, and especially the interaction between the two layers is studied. In order to resolve the complex 3D flow by means of hotwires a system for accurate automated traversing and data acquisition has been developed. In each flow case time-dependent measurements were taken in (X, Y, Z) space of about 3000 to 25,000 points, and it was found that the value of outlet velocity and the frequency of Kelvin — Helmholtz rolls have a clear influence on the size of the structures. Higher outlet velocities and higher frequencies of triggered two-dimensional roll-ups lead to a decrease in the size of longitudinal structures.     

Radiation Characteristics of Air in the Ultraviolet and Vacuum Ultraviolet Regions of the Spectrum behind the Front of Strong Shock Waves

Experiments on the measurement of air emission intensity behind the front of incident shock wave were carried out in a shock tube at an initial pressure of 0.25 Torr and shock wave velocities of 6.3–8.4 km/s. The emission intensity was measured in absolute units both in the form of an integral spectral distribution in a wavelength range of 120?400 nm (panoramic spectra) and as the time evolution of emission at the individual atomic lines of nitrogen and oxygen atoms. The results of the measurements demonstrated that the emission in air behind a shock wave in the vacuum ultraviolet region of 120–200 nm had a much higher radiation flux level than the emission in a range of 200–900 nm.     

Electrochemical properties and radical anions of carbocycle‐fluorinated quinoxalines and their substituted derivatives

Electrochemical reduction (ECR) and oxidation (ECO) of 5,6,7,8‐tetrafluoroquinoxaline ( 1 ) and its derivatives bearing various substituents R (7‐H ( 2 ), 7,8‐H₂ (3 ), 6‐CF₃ ( 4 ), 6‐Cl ( 5 ), 5,7‐Cl₂ ( 6 ), 5‐NH₂ ( 7 ), 6‐OCH₃ ( 8 ), 6,7‐(OCH₃)₂ ( 9 ), 6,7,8‐(OCH₃)₃ ( 10 ), 5,6,7,8‐(OCH₃)₄ ( 11 ), 6‐OCH₃,7‐N(CH₃)₂ ( 12 ), 6‐N(CH₃)₂ ( 13 ), 6,7‐(N(CH₃)₂)₂ ( 14 ), 5,6,7‐(N(CH₃)₂)₃ ( 15 ), and 7,8‐cyclo‐(=CF‐CF = CF‐CF=) ( 16 )) in the carbocycle have been studied by cyclic voltammetry in MeCN. For 1 – 4 and 7 – 15 , the first reduction peaks have been found to be 1‐electron and reversible, thus corresponding to the formation of their radical anions (RAs), which are long lived at 295 K except those of 4 – 6 and 15 , 16 . Irreversible hydrodechlorination has been observed for 5 and 6 at the first step of their ECR confirmed by EPR detection of corresponding RAs of 2 and 5,7‐H₂ derivative of 1 ( 17 ) at the next steps. Electrochemically generated RAs of 1 – 3 , 7 – 14 , and 17 have been characterized in MeCN by EPR spectroscopy together with DFT calculations at the (U)B3LYP/6‐31 + G(d) level of theory using PCM to describe the solvent. A noticeable alternation of spin density on the –NCCN– moiety of quinoxaline has been observed for all RAs possessing R‐substitution asymmetry. The comparative electron‐accepting ability of 1 – 15 has been analyzed in terms of their experimental reduction peak potentials and the (U)B3LYP/6‐31 + G(d)‐calculated gas‐phase first adiabatic electron affinities (EAs). The differences in electron transfer solvation energies for 1 – 15 have been evaluated on the basis of ECR peaks' potentials and calculated gas‐phase EAs. The ECO of 1 – 5 and 7 – 14 has been found to be irreversible.     

Common-path achromatic rotational-shearing coronagraph

To suppress starlight for direct exoplanet observation, we propose a common-path achromatic rotational-shearing coronagraph (CP-ARC), which is an interferocoronagraph with an angular-adjustable field rotator. The CP-ARC aims to maintain unwanted detection of stellar light, which can be suppressed incompletely by interference because of the finite diameter of the star. Compared to the previous interferocoronagraph, which had a nonadjustable 180° field rotation, the proposed CP-ARC can improve the coronagraphic contrast by several orders if the CP-ARC is combined with medium or large telescopes where the companion-star separation is optically resolved by more than a few Airy radii. The CP-ARC is made robust against mechanical disturbances due to the common-path interferometer principle.     

Bulk and Surface Quenching of Structural Steel: Morphological Analysis of the Structure

Structures formed in medium-carbon low-alloy steels during bulk quenching from furnace heating and surface quenching initiated by a low-power high-current electron beam are investigated by the methods of diffraction electron microscopy. The influence of the carbon concentration, initial austenite grain size, and cooling rate on the morphology of martensitic crystals and self-tempered carbide particles, long-range stress fields inside a packet and plates, and their dislocation substructure is analyzed. The temperature intervals for the formation of high-temperature plate martensitic crystals and packet (lath) martensite are estimated. It is demonstrated that the structure formed at ultrahigh heating and cooling rates is determined mostly by the morphology of martensite in the initial steel samples.     

On Effective Conductivity on ℤ d Lattice

We study the effective conductivity _e for a random wire problem on the d-dimensional cubic lattice ^d , d2 in the case when random conductivities on bonds are independent identically distributed random variables. We give exact expressions for the expansion of the effective conductivity in terms of the moments of the disorder parameter up to the 5th order. In the 2D case using the duality symmetry we also derive the 6th order expansion. We compare our results with the Bruggeman approximation and show that in the 2D case it coincides with the exact solution up to the terms of 4th order but deviates from it for the higher order terms.     

Manifestation of the nuclear anapole moment in the thallium M1 transitions

We calculate the nuclear spin-dependent parity-nonconserving E1 amplitudes for the optical transition 6p _{1/2, F} →6p _{3/2, F′} and hyperfine transition 6p _{1/2, F} →6p _{1/2, F′} in ²⁰⁵Tl. The experimental limit placed upon the former amplitude by Vetter et al. [PRL 74, 2658 (1995)] corresponds to the anapole moment constant κ_a=?0.26±0.27.     

Fractal description of significant nano-effects in polymer composites with nanosized fillers. Aggregation,phase interaction,and reinforcement

The paper analyzes experimental data obtained on physical and mechanical properties of nanostructured particle-reinforced composites with elastomer matrices and nano- and microsized carbon-containing particles by scanning probe microscopy and nanoindentation with specialized 3D computer processing. The nano-effects observed in the elastomer matrices are described using the fractal approach. A fractal model of nanoparticle aggregation in a polymer matrix is proposed. Phase interactions in the nanostructured polymer materials are described and fractal relations that predict the reinforcing effect of this type of media are presented. It is shown that interphase regions in the nanostructured composites are the same reinforcing elements as a nanofiller for the medium. It is found that reinforcement of elastomer composites by nanosized particles is a true nano-effect.