The ring puckering vibrations in trimethylene oxide and trimethylene sulphide as studied by P.M.R. spectroscopy in a liquid crystalline medium

The P.M.R. spectra of trimethylene oxide and trimethylene sulphide dissolved in a nematic solvent have been investigated. The chemical shifts, the direct and the indirect spin-spin couplings were determined.

The interpretation of the direct couplings in terms of the molecular structure shows that the ring skeleton of these molecules is not rigidly planar due to ring puckering vibrations. Mean amplitudes for the vibrations are estimated assuming fixed values for the bond distances and for the HCH bond angles. The results obtained are in good agreement with the earlier microwave studies.     

The vapor-phase Raman spectra and the ring-puckering vibration of some deuterated analogs of trimethylene oxide

The ring-puckering vibration has been observed in the Raman spectra of the vapor phase of several deuterated species of trimethylene oxide (α - d₂, β - d₂, α, α′ - d₄, and d₆). Only Δv = 2 transitions have a measurable Raman intensity. The line positions agree with infrared values to better than 0.5 cm⁻¹ in most cases and better than 1 cm⁻¹ in all cases. For all molecules the interpretation of the spectra is consistent with an essentially planar configuration having only a small barrier to inversion.     

Preparation and characterization of a lithium ion conducting electrolyte based on poly(trimethylene carbonate)

In this paper, the results of preliminary studies of two new solvent-free polymer electrolytes based on poly(trimethylene carbonate), p(TMC), with lithium trifluoromethanesulphonate, (triflate), and lithium perchlorate are described. Thin films of these electrolytes were obtained by evaporation of solvent from homogeneous mixtures of known masses of host polymer and salt. Electrolytes with compositions of n between 1.5 and 85, where n represents the molar ratio of (O=COCH₂CH₂CH₂O) units per lithium ion, have been prepared. These solvent-free electrolytes were characterized by measurements of total ionic conductivity, differential scanning calorimetry (DSC) and thermogravimetry (TGA). As expected from previous studies with these salts in poly(ethylene oxide), PEO, the triflate-based system showed superior thermal stability but with a lower total ionic conductivity than that of the perchlorate-containing electrolyte. The highest conductivity (approximately 3×10⁻⁴ Ω⁻¹ cm⁻¹) was found at 95°C with the electrolyte composition of (TMC)₂LiClO₄.     

Structure of Lennard–Jones nanowires encapsulated by carbon nanotubes

Molecular dynamics simulations have been performed to investigate the structures of Lennard–Jones(LJ) nanowires(NWs) encapsulated in carbon nanotubes(CNTs). We find that the structures of NWs in a small CNT only adopt multi-shell motifs, while the structures of NWs in a larger CNT tend to adopt various motifs. Among these structures, three of them have not been reported previously. The phase boundaries among these structures are obtained regarding filling fractions, as well as the interaction between NWs and CNTs.     

Creation and Investigation of Organic Light-Emitting Structures Containing Arrays of Colloidal Quantum Dots

We have created organic electroluminescent structures—ITO/TPD/Alq3/Al and ITO/PEDOT:PSS/TPD/Alq3/Al—which are organic light-emitting diodes (OLEDs). Experiments on the incorporation of CdSe/ZnS colloidal quantum dots into the active layer of the structure have been performed. The parameters of the created structures have been determined using optical-spectroscopy methods. The appropriateness of using the method of high-speed vacuum thermal deposition as a main method for the deposition of structural layers has been demonstrated, and the possibility of accelerated formation of layers of the material without disturbing its chemical structure has been shown. By measuring the photoluminescence spectra at different points in samples, we have determined the quality of the obtained structures and plotted maps of the radiation power distribution of the material and of its thickness. Recommendations for the creation of upper contacts and other regions of light-emitting structures have been formulated. We have created organic structures with ITO/PEDOT:PSS/TPD/TPD + CQD’s CdSe/Alq3/Al colloidal quantum dots, in which electroluminescence of CdSe/ZnS quantum dots has been obtained for a wide range of applied voltages. It has been shown that the introduction of colloidal quantum dots into the structure leads to a significant modification of its electroluminescence spectrum.     

Formation of nanodomain structures in lithium niobate as a result of pulsed laser irradiation

The surface nanodomain structures formed in lithium niobate single crystals as a result of pulsed irradiation of polar surfaces with UV and IR lasers have been investigated. The structures formed have been classified. The main features of the domain kinetics during one-dimensional growth at strong deviation from equilibrium have been revealed. A mechanism of polarization switching is proposed and discussed.     

Airy传递矩阵法与偏压下多势垒结构的准束缚能级

使用Airy函数和传递矩阵方法精确计算了一维定态薛定谔方程，并推广到多势垒结构，求解出有/无偏压作用的2,3势垒结构的准束缚能级，进一步研究了有/无偏压作用的2,3势垒结构的准束缚能级与有效质量和外加电压的关系，并对结论的正确性进行了验证． 另外，文中 还指出了有些文章中关于Airy传递矩阵法与计算偏压下多势垒结构的准束缚能级的错误陈述 . 关键词： 准束缚能级 有/无偏压作用的多势垒结构 Airy函数 透射系数     

Analysis of the Structure of Low-Lying States of Four-Boson Systems Based on Symmetry

The structure of inherent nodal surfaces of four-boson systems has been investigated. The most probable structures for each low-lying state have been found. A number of predictions on the structures of individual states and on the systematics of the spectra have been found. Received July 18, 1996; revised March 15, 1997; accepted in final form September 30, 1997     

Fermi-edge polaritons in Bragg multiple-quantum-well structures

The polariton propagation in one-dimensional photonic crystals and quasicrystals based on highly doped quantum-well structures has been theoretically studied. The superradiant and photonic crystal regimes have been considered and expressions for band gap edges for light waves in the Bragg structures have been obtained. The reflection and absorption spectra of such systems have been calculated and the so-called two-wave approximation to their study has been applied. The optical properties of the doped multiple-quantum-well structures are compared with those of undoped ones.     

Modifying a graphene layer by a thymine or a uracil nucleobase: DFT studies

The hybridizations of a graphene layer by a thymine and a uracil nucleobase have been investigated by performing density functional theory (DFT) calculations. The isolated and hybrid structures have been firstly stabilized to reach the minimum energy and the electronic properties have been subsequently evaluated for the optimized structures. The structural and atomic scale parameters indicated that the tip of graphene is important in determining the properties of new hybrids. Moreover, different effects of thymine and uracil nucleobases have been identified in the hybrid structures. Quadrupole coupling constants have been evaluated to characterize the atomic scale properties, in which the most notable effects of hybridizations have been observed for the atoms close to the linking regions whereas negligible effects have been seen for other atoms.     

Franck-Condon distribution in the 226 nm band of trimethylene sulfide

The potential function for the ring-puckering vibration of trimethylene sulfide in the lowest excited singlet state is obtained, and the relative intensity distribution in the 226 nm electronic transition calculated. It is concluded that the excitation of the ring-puckering vibration by itself does not account for the intensity of the higher energy peaks that are better assigned as combination bands of ring-puckering and CS stretching modes.     

The ring puckering vibration of trimethylene sulfoxide: Far-infrared spectrum from 50 to 675 cm−1

A number of absorptions between 100 and 300 cm^?1 in the infrared spectrum of trimethylene sulfoxide vapor have been observed and assigned to Δv_p = 1 and 2 transitions in the ring puckering mode. With the aid of a computer program providing for a potential function essentially of the form V(x) = V₂x² + V₃x³ + V₄x⁴ (x the dimensioned puckering coordinate), the barrier to inversion between the stable equatorial and a possible axial conformer is established to be 1205 cm^?1 with an uncertainty of ±11 cm^?1 at the worst or ±1 cm^?1 at best, depending upon the assignment of several very weak absorptions. The axial well depth, depending more critically upon these assignments, is no greater than 150 cm^?1 and may be as low as 5 cm^?1.     

Study of weakly-bound odd-A nuclei with quasiparticle blocking

The coordinate-space Hartree-Fock-Bogoliubov(HFB) approach with quasiparticle blocking has been applied to study the odd-A weakly bound nuclei ~(17,19)B and ~(37)Mg,in which halo structures have been reported in experiments.The Skyrme nuclear forces SLy4 and UNEDF1 have been adopted in our calculations.The results with and without blocking have been compared to demonstrate the emergence of deformed halo structures due to blocking effects.In our calculations,~(19)B and ~(37)Mg have remarkable features of deformed halos.     

High spin structures of 122Xe

High — spin states in ¹²²Xe have been investigated by γ ? γ coincidence measurements using the EUROGAM array. The reaction ⁹⁶Zr(³⁰Si,4n)¹²²Xe at a beam energy of 135 MeV was used to populate states of ¹²²Xe. The level scheme has been extended up to ～ 13.5 MeV and also enriched as compared to previous studies. New structures of competing dipole to quadrupole transitions have been observed. Experimental B(M1)/B(E2) ratios have been extracted for these structures and compared with theoretical estimates. They have also been compared with similar structures in Xe, Ba and Ce nuclei.     

钨酸铅晶体中与铅空位有关的电子结构和色心模型研究

根据密度泛函理论对钨酸铅晶体中铅空位周围的晶格进行了结构优化，计算得到铅空位周围的晶格结构、电子态密度分布和偏振吸收光谱；计算结果表明钨酸铅晶体中铅空位的两价负电性是通过铅空位周围的氧共同抓获两个空穴来维持局部电中性的，即铅空位周围形成的色心模型为［O₂^3--V_Pb^2--O₂^3-］，不同的氧离子抓获空穴方式不同形成不同的色心，对应不同的吸收带；根据吸收带的偏振性质，提出了各个 关键词： 钨酸铅晶体 色心模型 电子结构 偏振特性     

Ab initio crystal orbital calculations on polyacetylene-polyethylene copolymers

The band structures of polyacetylene-polyethylene copolymers of various compositions have been calculated. The results have been compared to the band structures of pure polyacetylene and polyethylene, and possible implications for molecular electronic devices have been discussed.     

Surface topography of laser annealed silicon

The topography of silicon has been studied by Nomarski and scanning electron microscopy and by light diffraction techniques. In addition to the previously known ripple structure with wavelength perpendicular to the laser E vector, two new ripple structures of other orientations have been found. The heights of the structures have been determined for the first time.     

The Golden Mean and self-similar structures in optics

Based on numerical modeling it has been found that if self-similarity (which often connects with the Golden proportions) is present in structures of Fibonacci gratings and multilayer systems, it appears in their optical characteristics. Properties of Fibonacci optical structures have been compared with those of other aperiodic systems. It has been shown that structures based on the Golden and Silver means have highly related optical properties.     

氢键对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响

本文在杂化密度泛函理论水平上研究了溶剂对2-(N-甲基)氨基-5-硝基吡啶分子非线性光学性质的影响.在溶剂中,构造了包括氢键作用的超分子体系,在优化结构的基础上分别研究了由极化连续模型模拟的溶剂与该分子的长程相互作用、溶剂与该分子的氢键相互作用以及溶剂与包括氢键作用的超分子体系整体的相互作用对分子的几何结构、非线性光学性质、紫外吸收光谱和电荷分布等特性的影响.结果表明,溶剂中分子电偶极矩、线性极化率和第一超极化率都增大,而溶剂与溶质分子通过氢键形成的超分子结构与单体有着明显区别.因此,氢键对分子结构和性质的影响较大,从而将明显的影响该类分子的非线性光学性质.