红外光谱对碱土金属二元羧酸盐结构的研究

研究了三十种二元羧酸金属盐的红外光谱，讨论了金属离子和二元酸的种类对二元酸盐配位结构的影响。发现Mg盐、Ba盐，Sr盐为螯合配位，Ca盐，Zn盐中同时存在螯合配位和桥式配位，二元酸的种类对羧酸盐配位结构没有影响。对羧酸盐在常温和熔融后的栩位方式和结构上的差异的研究结果表明，Mg盐，Ca盐与Sr盐，Ba盐在熔融后的结构变化不同。     

类Kerr介质中双模SU(1,1)相干态场与Λ型三能级原子相互作用的量子统计性质

导出了类Kerr介质中双模SU(1,1)相干态场与Λ型三能级原子相互作用系统的态函数,研究了Kerr效应对Λ型三能级原子布居概率、双模SU(1,1)相干态场的互关联函数、Cauchy-Schwartz不等式及二阶相干度的影响.结果表明:Kerr效应使原子与光场的耦合减弱,原子布居的崩塌与复苏的周期缩短;在初始光场较弱和较强两种情况下,类Kerr介质对双模SU(1,1)相干态场两模间的相关性、相关程度以及光子的聚束与反聚束效应产生的作用有明显的区别.     

NO-2-I-体系双波长紫外分光光度法测定痕量亚硝酸根

在稀盐酸介质中,亚硝酸根氧化碘化钾的反应产物I-3在288nm和352nm处有两个强吸收峰.基于此建立了双波长紫外分光光度法测定痕量NO-2的新方法.该法简便、快速、选择性好,线性范围为0-0.4μg/mL,检出限为3.4×10-9g/mL.用于河水、井水、矿泉水中亚硝酸根的测定,结果令人满意.     

Controlling global stochasticity of Hamiltonian systems by nonlinear perturbation

A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust against small external noise. The mechanism underlying this high control efficiency is intuitively explained. Received 15 January 2002 Published online 6 June 2002     

Reception of a Signal with Unknown Duration

The maximum likely and optimal (Bayesian) algorithms for detecting an arbitrary-shaped signal observed against the background of Gaussian white noise and for measuring the duration are synthesized. Exact expressions for the characteristics of the maximum likely algorithms are found. The characteristics of the Bayesian algorithms are obtained using computer simulations.     

Spontaneous formation of a system of highly ordered germanium nanoislands upon epitaxial deposition on profiled (111) silicon substrates under electromigration conditions

Atomic-force microscopy was used to study the surface topography of SiGe structures grown by epitaxial deposition of Ge on profiled Si(111) substrates under electromigration conditions. Systems of highly ordered germanium nanosized islands with dimensions of 10–20 nm and a density of 6×10¹⁰ cm^?2 were obtained. It is shown that the geometrical parameters of self-organizing nanoislands can be controlled by a proper choice of the growth and postgrowth annealing conditions for these structures.     

Synthesis, structure and optical properties of Eu/TiO2 nanocrystals at room temperature

The nanocrystal samples of titanium dioxide doped with europium ion (Eu³⁺/TiO₂ nanocrystal) are synthesized by the sol-gel method with hydrothermal treatment. The Eu³⁺ contents (molar ratio) in the samples are 0, 0.5%, 1%, 2%, 3% and 4%. The X-ray diffraction, UV-Vis spectroscopy data and scanning electron microscope image show that crystallite size is reduced by the doping of Eu³⁺ into TiO₂. Comparing the Raman spectra of TiO₂ with Eu³⁺/TiO₂ (molar ratio Eu³⁺/TiO₂=1%, 2% and 4%) nanocrystals at different annealing temperatures indicates that the anatase-to-rutile phase transformation temperatures of Eu³⁺/TiO₂ nanocrystals are higher than that of TiO₂. This is due to the formation of Eu-O-Ti bonds on the surface of the TiO₂ crystallite, as characterized by the X-ray photoelectron spectroscopy. The photoluminescence spectra of TiO₂ in Eu³⁺/TiO₂ nanocrystals are interpreted by the surface self-trapped and defect-trapped exciton relaxation. The photoluminescence of Eu³⁺ in Eu³⁺/TiO₂ nanocrystals has the strongest emission intensity at 2% of Eu³⁺ concentration.     

Isoelectric focusing sample injection for capillary zone electrophoresis in a fused silica capillary.

An improvement has been made to couple isoelectric focusing (IEF) sample injection and capillary zone electrophoresis in an untreated fused silica capillary. Electroosmotic flow is efficiently prevented by simply using a rubber block at the outlet end of the capillary during IEF sample injection. The experimental conditions that affect the concentration effect are discussed. A concentration enhancement factor of over 100-fold can be easily obtained for two model proteins: lysozyme and ribonuclease A.     

Temperature dependence of interband transition energy in InGaAsN strain-compensated quantum-well and ridge-waveguide lasers fabricated with pulsed anodic oxidation

Ridge-waveguide InGaAsN triple-quantum-well strain-compensated lasers grown by metal organic chemical vapor deposition were fabricated with pulsed anodic oxidation. The laser’s output power reached 145 mW in continuous-wave mode at room temperature for a 4-?m -stripe-width laser. Continuous-wave single longitudinal mode operation was maintained at a high injection current level with a wavelength of 1287.3 nm at room temperature. Single longitudinal mode operation at 1317.2 nm was achieved at twice the threshold current at 100 °C. The band gap of InGaAsN in the quantum wells at different temperatures was calculated and compared to the measured temperature-dependent laser wavelength.     

Fermi surface and thermoelectric power of (Bi1−x Sbx)2Te3<Ag, Sn> mixed crystals

The Fermi surface anisotropy of (Bi_1?x Sb_x)₂Te₃ single crystals (0.25 ≤ x ≤ 1) was studied by analyzing the angular dependence of the frequency of Shubnikov-de Haas oscillations and the effect of tin and silver doping on the thermoelectric power in these crystals in the temperature range 77 ≤ T ≤ 300 K. It was shown that silver doping of (Bi_1?x Sb_x)₂Te₃ mixed crystals produces acceptors, while silver in Bi₂Te₃ acts as a donor. Tin also exhibits acceptor properties. Both tin and silver doping of p-(Bi_1?x Sb_x)₂Te₃ mixed crystals decrease the thermoelectric power due to an increase in the hole concentration.