Spatial coherences of the sound pressure and the particle velocity in underwater ambient noise

The spatial coherences were investigated between the sound pressure and the three orthogonal components of the particle velocity in underwater ambient noise. Based on the ray theory, integral expression was derived for the spatial coherence matrix of the sound pressure and the particle velocity in a stratified ocean with dipole noise sources homogenously distributed on the surface. The integrand includes a multiplying factor of the vertical directivity of the noise intensity, and the layered ocean environment affects the spatial coherences via this directivity factor. For a shallow water environment and a semi-infinite homogenous medium, the coherence calculation results were given. It was showed that the sound speed profile and the sea bottom could not be neglected in determining the spatial coherences of the ambient noise vector field.     

p-Wave Feshbach molecules

We have produced and detected molecules using a p-wave Feshbach resonance between 40K atoms. We have measured the binding energy and lifetime for these molecules and we find that the binding energy scales approximately linearly with the magnetic field near the resonance. The lifetime of bound p-wave molecules is measured to be 1.0+/-0.1 ms and 2.3+/-0.2 ms for the ml=+/-1 and ml=0 angular momentum projections, respectively. At magnetic fields above the resonance, we detect quasibound molecules whose lifetime is set by the tunneling rate through the centrifugal barrier.     

Experimental long-distance decoy-state quantum key distribution based on polarization encoding

We demonstrate the decoy-state quantum key distribution (QKD) with one-way quantum communication in polarization space over 102 km. Further, we simplify the experimental setup and use only one detector to implement the one-way decoy-state QKD over 75 km, with the advantage to overcome the security loopholes due to the efficiency mismatch of detectors. Our experimental implementation can really offer the unconditionally secure final keys. We use 3 different intensities of 0, 0.2, and 0.6 for the light sources in our experiment. In order to eliminate the influences of polarization mode dispersion in the long-distance single-mode optical fiber, an automatic polarization compensation system is utilized to implement the active compensation.     

Negative refraction of complex lattices of dielectric cylinders

Some photonic crystals (PCs) consisting of complex lattices of dielectric cylinders can have an effective refraction index (neff$n_{\mathrm{eff}}$) of −1. Subwavelength imaging by a slab of a honeycomb PC of dielectric cylinders with neff=−1$n_{\mathrm{eff}}=-1$ is investigated and an open resonator with a quality factor higher than 3000 is designed with the same PC. Air–PC interfaces with low reflection are also used for the slab lens and open resonator.     

Synthesis and luminescent properties of nanoparticles GdCaAl3O7:RE (RE=Eu, Tb) via the sol-gel method

By using metal nitrates as starting materials and citric acid as complexing agent, GdCaAl₃O₇:Eu³⁺ and GdCaAl₃O₇:Tb³⁺ powder phosphors were prepared by a citrate-gel method. Thermal analysis (TG-DTG), X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM), photoluminescence excitation and emission, as well as kinetic decays were employed to characterize the resulting samples. The results of the XRD indicated the precursor samples began to crystallize at 800 °C and the crystallinity increased with elevation the annealing temperature. TEM images showed that the phosphor particles were basically of spherical shape, with good dispersion about a particle size of around 40-70 nm. Upon excitation with UV irradiation, it is shown that there is a strong emission at around 617 nm corresponding to the forced electric dipole ⁵D₀-⁷F₂ transition of Eu³⁺, and at around 543 nm corresponding to the ⁵D₄-⁷F₅ transition of Tb³⁺. The dependence of photoluminescence intensity on Eu³⁺ (or Tb³⁺) concentration and annealing temperature were also studied in detail.     

采用瞬态电致发光研究磷光掺杂体系发光瞬时过冲的发射机理

掺杂型有机电致发光器件中载流子累积、载流子复合等物理过程的深入了解对提高器件效率和稳定性有重要作用。通过瞬态电致发光测量可以研究掺杂型有机电致发光器件内部载流子累积。对结构为: ITO/NPB(30 nm)/host: Ir(ppy)₃/BCP(10 nm)/Alq₃(20 nm)/LiF(0.7 nm)/Al(100 nm)的器件分别研究主体材料以及客体掺杂浓度变化对有机掺杂型器件瞬态发光行为的影响。实验发现,当单脉冲驱动电压关闭后,只有TAZ: Ir(ppy)₃掺杂器件出现发光瞬时过冲现象,即发光强度衰减到一定时间时突然增强;且随着客体掺杂浓度的增加,瞬时过冲强度逐渐增强。通过分析TAZ: Ir(ppy)₃掺杂器件的瞬时过冲强度对主体材料与掺杂浓度的依赖关系,进一步发现,瞬时过冲效应强度主要受限于发光层内部积累的电子载流子;TAZ: Ir(ppy)₃发光层内电子容易被客体材料分子俘获并积累,电场突变时陷阱电子容易跳跃到主体材料上并与主体材料上积累的空穴形成激子,激子能量传递到客体材料上并复合发光继而出现发光强度的瞬时过冲现象。研究发光瞬时过冲行为可探究器件发光层内的载流子和激子的动态行为,有利于指导器件的设计,从而减少积累电荷的影响,提高器件的性能。     

Theoretical research on the spin-Hamiltonian parameters of the square-planar CuS46− clusters in Cu(II)–dithiophosphonate complexes

The spin-Hamiltonian parameters (g-factors g_//, g_⊥ and hyperfine structure constants A_//, A_⊥) of the square-planar CuS^{6 ?}₄ clusters in Cu(II)–bis [4-ethoxphenyl-O-alkyl]-dithiophosphonate complexes are computed with the high-order perturbation formulas based on the two-mechanism model. The model includes the contributions to spin-Hamiltonian parameters from the vastly-utilised crystal-field (CF) mechanism concerning the CF excited states and the generally-omitted charge-transfer (CT) mechanism due to CT excited states. The energy levels of CF and CT excited states needed in the calculation are obtained from the observed optical spectra. The calculated results are in rational accordance with the experimental values. The signs of constants A_// and A_⊥ are suggested and the reasons of the very small g-shifts |?g_i| (= | g_i ? g_e |, where g_e ≈ 2.0023 and i = // or ⊥) are discussed.     

Role of cationic gemini surfactants toward enhanced ninhydrin–tryptophan reaction

In this paper we report the effect of dicationic ‘gemini’ surfactants (CH₃)₂C₁₆H₃₃N⁺? (CH₂)_m? N⁺C₁₆H₃₃(CH₃)₂, 2Br^? (where m = 4, 5, 6) on the reaction of ninhydrin with DL ‐tryptophan. The gemini surfactant micellar media are comparatively more effective than their conventional monomeric counterpart cetyltrimethylammonium bromide (CTAB) micelles. Also, whereas typical rate constant (k_ψ) increase and leveling‐off regions, just like CTAB, are observed with geminis, the latter produce a third region of increasing k_ψ at higher concentrations. These subsequent increases are ascribed to changes in micellar morphologies, consistent with changes in ¹H NMR line widths. Quantitative kinetic analysis of the rate constant–[surfactant] data has been performed on the basis of modified pseudophase model. Copyright © 2007 John Wiley & Sons, Ltd.     

Interpretation of Light Scattering Spectra of Dispersions – A Hybrid Approach to Account for Interparticle Interactions

The problem of extracting quantitative information on individual particle properties from spectroscopic measurements conducted at concentrations where particle interactions become significant is of great industrial and theoretical importance. For dispersions of charged particles, this can happen at fairly low concentrations. The effect of the fluid (slurry) structure has to be taken into account to interpret the light scattering spectra of such dispersions. In this paper, a hybrid method that addresses the effect of the fluid structure is proposed. The hybrid approach describes the fluid structure by relating the “effective” Percus‐Yevick hard‐sphere parameters to the system parameters using empirical models. The feasibility of this approach is examined through a theoretical study with data generated by Monte Carlo simulations of a monodisperse dispersion of charged spherical particles using realistic interaction potentials under single scattering conditions.     

GISAXS study of carbon nanotubes grown by CVD

We report a quantitative Grazing Incidence Small Angle X‐ray Scattering (GISAXS) study of a dense film of mutually oriented carbon nanotubes (CNTs) grown by a catalytically‐activated DC HF CCVD process after dispersion of metallic catalytic (Co) islands on SiO₂/Si(100) substrates. The GISAXS pattern analysis is expanded to non‐correlated surface science systems and is based on CNTs density, characteristic lengths, atomic Co dispersion throughout the CNTs and roughnesses of uncorrelated particles. The results are closely compared to SEM and TEM observations. The GISAXS patterns, even dominated by envelope features of disordered objects, provide significant complementary quantitative data about CNTs films. The results underline that cobalt continuously fills the nanotube in the course of the growth and that the CNTs experience a large tendency toward mutual alignment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)