Properties of renormalized spectrum of interacting with polarization phonons localized quasiparticle with degenerated excited state

Abstract

The quantum theory of renormalized energy spectrum of the system of localized two-level quasiparticle, with degenerated spectrum, interacting with polarization phonons, being the model of multilayered nanostructure, is developed within the modified Feynman-Pines diagram technique. Effectively taking into account the multi-phonon processes, the theory is valid in a wide range of energies which contains the main states and the satellite groups of energies produced by the resonant bound-to-phonons states of quasiparticle in the vicinity of the threshold energies of their radiation. The properties of renormalized spectrum of the system are analyzed and dependences of the widths of groups of energy levels (main and satellite) on the magnitudes of inter-level coupling constants are obtained.     

Facile synthetic route to benzo[c]chromenones and thieno[2,3-c]chromenones

Convenient two-step procedure for the synthesis of fused chromenone derivatives was developed. Reduction of the obtained in the Meerwein arylation reaction aryl- and thienylquinones allowed to construct 6H-benzo[c]chromene-6-ones and 4H-thieno[2,3-c]chromen-4-one in a more cost- and time-effective manner in comparison with already known methods. The obtained products have provided a new entry to chromenone derivatives.     

Stable nonequilibrium composites based on liquid-crystalline polymers and cadmium selenide nanoparticles

On the basis of copolymers of 4-methoxyphenyl-4-(6-(acryloyloxyhexyloxy)benzoate with 4-(6-acryloyloxyhexyloxy)benzoic acid, nonequilibrium composites containing nanoparticles (quantum dots) of cadmium selenide at concentrations many times higher than their solubility limit in the liquid-crystalline phase are synthesized. In the resulting material, the polymer matrix undergoes the transition to the liquidcrystalline state before separation into phases with concentrations of nanoparticles corresponding to thermodynamically equilibrium values. Under common conditions, the composites are stable for at least several months.     

Synthesis of 3‐Aryl/methoxycarbonyl‐3,4‐dihydroisocoumarin‐6‐carboxylic Acid Derivatives

3‐Substituted methyl 3,4‐dihydroisocoumarin‐6‐carboxylates were obtained by the intramolecular cyclization of 2,5‐dimethoxycarbonyl benzenediazonium bromides with methyl/ethyl acrylate and styrenes under Meerwein's arylation conditions.     

Vacancy generation in silicon in the temperature range 100–633 K under electron irradiation

The processes of radiation defect formation in Si with 1 MeV electron irradiation in the temperature range 100–633 K have been investigated. It is established that the generation efficiency of vacancies λ_V increases with temperature, then starts to saturate at temperatures of 250 K and finally stays constant at T>300 K. It is shown that at high temperatures, the λ_V dependence can be caused by the additional scattering of “hot” interstitial atoms on acoustical and optical phonons, the numbers of which increase with the temperature. An explanation, based on the creation of quasi-molecule of “hot” interstitial and lattice atoms, is proposed.     

Solvent effect on the structure of composite films obtained from chitosan solutions with a precursor of silver nanoparticles

The solvent effect on the structure of nanocomposite films cast from chitosan solutions with AgNO₃ as a precursor of silver nanoparticles was studied for the first time. The size and concentration of silver nanoparticles in the chitosan matrix can be controlled by varying the chitosan-dissolving ability of the solvent with carbonic acid.     

Design of terahertz-bandwidth arbitrary-order temporal differentiators based on long-period fiber gratings

We show that long-period fiber grating (LPG) incorporating N-1pi-phase shifts can serve as an Nth order temporal differentiator that operates in transmission. Due to the inherent large bandwidth provided by LPGs, subpicosecond (terahertz-bandwidth) optical signals may be processed with centimeters-length devices. Design parameters for up to fifth-order differentiators are given.