Spectral–kinetic characteristics of the F2 laser transition

A theoretical model for the F₂(D–A) laser transitions is built. The model includes a scheme of the main laser transitions proposed. A value of the radiative lifetime of the upper laser level in the conventional kinetic models of the F₂ laser is proved to be underestimated by one order of magnitude. A general theory of steady-state light amplification in a molecular laser with non-equilibrium vibrational distribution is developed. Relations of the small-signal gain and the saturating energy flux with parameters of molecular electronic–vibrational kinetics are established. The theory is applied to explain properties of F₂ laser amplifiers. PACS 31.70.Hq; 42.55.Lt     

Polaron States of 3,4-Ethylenedioxythiophene Oligomers

Theoretical and Experimental Chemistry - The electronic and spatial structure of 3,4-ethylenedioxythiophene oligomer containing 12 units (E12) in 0, +1, +2, +3, and +4 charge states has been...     

Quantum-chemical modelling of the reactivity of charcoal surface double bonds

LCAO MO SCF calculations using the 3-21G basis were used to study the electronic and three-dimensional structure of several polycyclic aromatic hydrocarbons as models for the surface of activated charcoal. Localized carbon-carbon double bonds capable of adding electrophilic reagents were found on the periphery of these molecules. The reactivity of the peripheral C=C bonds was evaluated relative to consecutive bromination reactions of the C₅₄H₁₈ molecule. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 1, pp. 30–34, January–February, 2008.     

Suppression of coherent population trapping upon spontaneous decay of an excited state

The interaction of a model three-level Λ system with electromagnetic radiation is considered under the conditions where a coherence (an off-diagonal matrix element) between lower sublevels arises upon spontaneous decay of an excited state. The cases of bichromatic and incoherent broadband fields are analyzed. It is shown that the occurrence of coherence may significantly change the character of evolution of the system under study with time. These changes are most pronounced for broadband fields. Some features of this phenomenon are considered for multilevel atomic systems.     

Analysis of the Properties of Carbon Nanotubes from Distribution Maps of Molecular Electrostatic Potential

The electronic structure and stereochemical structure of some types of carbon nanotubes were investigated by quantum-chemical methods. It was found that the "zigzag" configurations have significant dipole moments and are characterized by dimorphism, reflected in the existence of symmetrical and unsymmetrical states.     

Thermal transport of oil and polymer composites filled with carbon nanotubes

We studied the thermal transport properties of multi-walled carbon nanotubes (MWNTs) in polymer and oil matrices. The thermal conductivity of the oils and polymers increased linearly when adding tubes. We observe a particularly high increase in the thermal diffusivity of carbon-nanotube-loaded liquid crystal polymers (6×10⁻⁵ cm²/s wt%), which is due to a spontaneous alignment of the MWNTs. Carbon nanotubes increased the thermal conductivity of oil by a factor of three for 20 wt% loading. We found little or no dependence of the thermal enhancement on the specific flavor of multiwall nanotubes used in the composites. Carbon nanotubes are excellent nanoscale fillers for composites in thermal management application.     

Functionalization of latex particle surface by using polymeric inisurfs

In this work the emulsion polymerisation of styrene was carried out in presence of the inisurfs (reactive surfactants). The reaction kinetics was followed by dilatometric and calorimetric measurements. The influence of the inisurf concentration in reaction mixture as well as the reaction temperature on the particle properties were studied. Resulting particles were characterised with FFFF‐MALLS and PCS. Viscosity measurements indicate the formation of particle flocks in the solution at certain inisurf concentration in reaction mixture.     

Coherent backscattering under conditions of pulsed radiation trapping

Coherent backscattering of pulsed radiation emitted by optically dense atomic ensembles is considered. The diagrammatic technique is used for deriving analytic expressions for correlation functions of scattered light, which make it possible to take into account all main factors affecting the dynamics of the process, including the hyperfine and Zeeman structure of the ground and first excited states of atoms, polarization of probe radiation, the actual shape and size of an atomic cloud, its spatial inhomogeneity, motion of atoms, and angular-momentum polarization of atoms. On the basis of these relations, the time dependence of the total intensity and the dependence of enhancement factor of backscattered light on the pulse duration, type of polarization of the polarization system of observation, optical thickness of the scattering medium, and the carrier frequency of the pulse are investigated. The calculations are performed for an ensemble of rubidium-85 atoms cooled in magnetooptical traps.     

Statistical Properties of Conduction Electrons in an Isolated Metal Nanosphere

We explore differences between canonical and grand canonical ensembles of 500–2000 free electrons confined in a spherical well with a radius from 1.2 to 2 nm. The averaged occupation numbers of the electronic energy levels and their variances are calculated. For isolated Ag and Au particles, the sum of the variances of all occupation numbers differs from the corresponding bulk-metal value by a factor of 0.005 to 2.     

Some characteristics of resonant electromagnetic modes in a dielectric sphere

A set of formulae have been developed for calculations of the optical characteristics of droplets under conditions of whispering gallery mode (WGM) excitation. The WGM excitation is shown to cause the ripple structure in the Mie extinction cross section. The Chýlek equation for the distance between two neighboring morphology-dependent resonances (MDRs) in a spectrum has been revised. The equation is presented for the spherical-resonator finesse allowing for light scattering on inhomogeneities of the resonator surface, etc. A comparison of the theory and data in the literature is made and some peculiarities of spectra are explained.