Molecular Alignment Induced by Ultrashort Laser Pulses and Its Impact on Molecular Motion

Spectroscopy aims at extracting information about matter through its interaction with light. However, when performed on gas and liquid phases as well as solid phases lacking long-range order, the extracted spectroscopic features are in fact averaged over the molecular isotropic angular distributions. The reason is that light–matter processes depend on the angle between the transitional molecular dipole and the polarization of the light interacting with it. This understanding gave birth to the constantly expanding field of “laser-induced molecular alignment”. In this paper, we attempt to guide the readers through our involvement (both experimental and theoretical) in this field in the last few years. We start with the basic phenomenon of molecular alignment induced by a single pulse, continue with selective alignment of close molecular species and unidirectional molecular rotation induced by two time-delayed pulses, and lead up to novel schemes for manipulating the spatial distributions of molecular samples through rotationally controlled scattering off inhomogeneous fields and surfaces.     

Upgrading the industrial process flowsheet for the dehydration of methylbutenes to isoprene. II: Analysis of plant test results and industrial implementation of the upgraded design

Pilot tests of technology for the dehydration of methylbutenes to isoprene are performed in a tworeactor system with an additional supply of an overheated gas into the interreactor space. The tests are performed on a pilot plant with two adiabatic reactors. The total volume of the catalyst charge is 60 dm³, the temperatures are 565–620°С, the contact time is 0.18–0.25 s, the raw material is diluted with steam in a weight ratio of С₅Н₁₀: Н₂О = 1.0: (6.0–30.0), and the excess pressure is 0.6–0.7 kgf/cm². The dependence of the isoprene concentration in the contact gas on the heat energy supplied by the raw material and steam is determined under conventional conditions of the process and in a pseudo-isothermal mode via an additional supply of overheated gas into the interreactor space. It is shown that the isoprene yield is increased by 10–12% by using the upgraded mode. The conditions for conducting the industrial process are determined based on the obtained results. After upgrading the design, tests are performed at the synthetic rubber factory of PAO Nizhnekamskneftekhim on a plant for the dehydrogenation of methylbutenes in the reactor with a doublelayer catalyst bed (nine tons per layer). The patterns established during the pilot tests generally prove to be true, but the selectivity of the process is reduced due to a number of design flaws. Corrective measures are outlined. Comparison of the experimental results and the calculated values confirm the accuracy of the mathematical model.     

Peculiar electric properties of polarized layer in alkaline silicate glasses

Broadband dielectric spectroscopy (BDS) was applied to study polarization phenomena in alkaline silicate glasses, in particular, properties and structure of subsurface (anodic) polarized layers forming in poling with deposited film electrodes of different structures. A model of poled glasses which does not contradict experimental data is proposed. In accordance with the model, a poled glass is presented as two resistor-capacitor circuits in a series connection, one of which is the polarized layer and another is the rest of the sample. It is found that the electric properties of the layers essentially depend on the structure of the anodic electrode used in glass poling. It is also shown that the dielectric response of poled glass samples is mainly determined by the electric properties of the submicron polarized layers and this gives an opportunity to reveal specific properties of the layers rather than ones of the glass sample bulk. Revealed temperature dependence of DC conductivity of the polarized layers obeys Arrhenius's law, and determining activation energy does not depend on the electrode. Finally, it is noted that today above-mentioned information about polarized layers can be obtained only by BDS.     

Proper and Improper Complex Waves of a Circular Two-Layer Screened Waveguide with an Axial Longitudinally Magnetized Ferrite Layer

In a two-layer circular screened waveguide with a longitudinally magnetized inner ferrite layer, the presence of different types of complex waves (CWs) both satisfying and not satisfying the energetic orthogonality condition is shown. The CWs are the solutions of a homogeneous boundary value problem, but, in the first case, the waves are energetically independent and, in the second case, they are associated with the source and indirectly coupled through it.     

Techniques for estimating the power of the intermodulation interferences of orthogonal frequency-division multiplexing signals

The techniques for estimating the powers of intermodulation interferences (the total power of interferences and the interference power within the signal band), which correspond to orthogonal frequency-division multiplexing (OFDM) signals at the output of a transmitter interpreted as an inertialess nonlinear device, are described.     

Results from tests of the P-67 boiler used as part of a 800-MW power unit

Results from the balance tests of a retrofitted P-67 boiler carried out in the period 2006–2008 are presented. The tests involved assessment of the change with time of the heating-surface thermal efficiency coefficients in running the power unit at its base loads in the range 740–800 MW, with seven to eight coarsegrinding mills switched into operation, with the open and closed gate values installed in the channels supplying air-powder mixture to the fourth-tier burners, and with the fraction of air supplied for lower blasting equal to 5–7% and that for the startup burners, 2%. The combined cleaning system operated in its design mode with additional blowing operations according to special control signals. The furnace waterwalls and the convective shaft surfaces were subjected to mechanical cleaning every year during current repairs.     

Development of Saturable Absorbers for Laser Passive Q‐Switching near 1.5 μm Based on Transparent Ceramic Co2+:MgAl2O4

We describe the development of a reasonable cost Co²⁺:MgAl₂O₄ transparent ceramic plates fabrication technology that allows the producing of parts functioning as passive laser Q‐switches in the 1.3–1.7 μm domain. The main relevant material characteristics were measured. The absorption band, positioned between 1.2 and 1.7 μm, is typical of the ⁴A₂ (⁴F) → ⁴T₁ (⁴F) transition of Co²⁺ substituting Mg²⁺ ions in their T_d symmetry sites. The measured ground‐state absorption cross section σ_gs = 2.9 × 10^?19 cm², saturation contrast γ = 0.12, and depleted ground‐state recovery time τ₂ = 110–430 ns render such parts suitable for the intended application. The radiative lifetime was estimated as . The spin‐orbit splitting constant was estimated as ξ_SL??150 cm^?1 for the ⁴F parent ground state, and ξ_SL ? –575 cm^?1 for the ⁴P parent excited state. Obtained specimens had a transmission of ~80% (t = 2 mm, λ = 600 nm) and included some opaque, white spots. Further improvement of host optical transmission and resistance to laser damage are necessary.     

A study of the initial stages of iron passivation in neutral solutions using the quartz crystal resonator technique

The initial period of growth of a passive film of iron in borate solutions (pH 7.4 and 6.7) is studied using the quartz crystal resonator technique (EQSN) and pulsed chronoamperometry. Dependences of the surface layer thickness on time are obtained at the metal passivation and prepassivation potentials. Regions corresponding to different stages of passive layer formation are found in anodic current transients, which allowed the ambiguous effect of atomic hydrogen on kinetics of hydrogenated iron dissolution to be explained. It is shown that the iron hydrogenation promoter prevents formation of a primary passive film by accelerating iron dissolution at prepassivation potentials.