Excitons in highly optically excited gallium phosphide

A study has been made of luminescence in weakly (10¹⁵-10¹⁶ cm^-3) and heavily (10¹⁸-10¹⁹ cm^-3) N-doped GaP crystals induced by 1.78, 2.34 and 3.56 eV photons from Q-switched ruby or neodymium lasers with a KDP crystal for second harmonic generation. The results which were obtained at excitations up to 10²⁰ cm^-3 electron-hole pairs are interpreted as the transitions: single bound excitons, bound excitonic molecules, free excitons in weakly-doped GaP, as well as Auger processes and the formation of a new excitonic state similar to a solid metal with high density of single excitons and excitonic molecules bound to isoelectronic traps in heavily-doped GaP.     

Superheating in linear polymers studied by ultrafast nanocalorimetry

To study phase transition kinetics on submillisecond time scale a sensitive ultrafast nanocalorimeter was constructed. Controlled ultrafast cooling, as well as heating, up to 10⁶K/s was attained. The method was applied for the measurements of the superheating phenomenon in a set of linear polymers: iPS, PBT, PET, and iPP. A power law relation between the superheating and the heating rate holds in the heating rate range 10^-2-10⁴K/s. A limiting superheating of about 10% of the melting temperature was observed at rates above 10⁴-10⁵K/s. This limit depends on annealing conditions before sample melting. The observed superheating limit, as well as the power law, can be accounted for the internal stresses near the crystalline amorphous interface in semicrystalline polymers induced by heating, which are related to the thermal expansion gradients inherent in a semicrystalline material.     

Synthesis and Characterization of New Light Emitter Symmetrical Phenoxazinium Salt and Its Potential Application as Sensor for Assessment of Hg2+

The sensitization of the excited triplet state of a novel symmetrical Bis(dialkylamino)phenoxazinium salt was developed in the presence of Hg²⁺. This effect was used to determine the concentration of Hg²⁺ in different water samples. The phenoxazinium salt sensor was characterized by different spectroscopic tools such as: UV, FTIR, NMR and fluorescence spectra. The sensor has an emission band at 347 nm in DMSO. Hg²⁺ in DMSO at pH 5.6 can remarkably quench the fluorescence intensity of the sensor at 347 nm and a new band was appeared at 436 nm due to the strong complex formation between Hg²⁺ and sensor. The quenching of the band intensity at 347 and the enhancement of the intensity of the new band at 436 were used to determine the Hg²⁺ in different waste water samples. The dynamic range found for the determination of Hg²⁺ concentration is 8.7?×?10^-10 – 1.4?×?10^-6 mol L^?1 with a detection limit of 5.8?×?10^?10 mol L^?1 and quantification detection limit of 1.8?×?10^-9 mol L^-1.     

Gamma-ray solid laser: ion-optical system for fasthigh-quality focusing of powerful non-paraxial ion beams of largeformat enriched with excited nuclei

An ion-optical system (IOS) for fast high-quality focusing of powerful paraxial ion beams of large format is suggested. Such beams could be enriched in excited short-lived (10^-4-10^-6 s) laser-active nuclei (ELAN). To increase the beam power, ions are collected from the visible surface (10-10⁴ cm²) of an intermediate target (converter). The full converter surface is enhanced by a factor of 10²-10⁴ by a special micro-relief and achieves 10³-10⁷ m². The toms containing ELAN are created in the converter by a powerful radiation source using neutrons, γ quanta, charged particles, etc. Those ELAN atoms are emitted from the converter surface and selectively ionized by a dye laser just above the surface. Using a specially chosen emitter (converter) shape, a paraxial ion beam is formed. This is due to the micro-relief structure of the emitter surface, its high-quality orientation, and cylindrical (instead of spherical) ion optics. In the vicinity of an active medium (AM) for a gamma-ray laser, the ions are decelerated so that they can penetrate only into 1-3 outer layers of the host matrix, e.g., diamond. This makes heating of the AM by the ion beam negligible in comparison to self-heating due to internal conversion. Analytical and numerical estimation of the IOS aberrations have shown that the compression of the ion beam exceeds10⁵-10⁶, and that a considerable part (10%) of the ELAN reach the AM in a time as short as10^-7 s. This ensures the rapid and controllable deposition of ELAN into an AM within a gamma-laser system based on existing techniques without using nuclear explosions. This revised version was published online in August 2006 with corrections to the Cover Date.     

The kinetics of the sensitized flourescence of naphthalene single crystals doped with 2-methylnaphthalene and anthracene

The kinetics of the sensitized flourescence in naphthalene crystals doped with 2-methylnaphthalene (2-MN) and anthracene (A) was studied as a function of the temperature. These experiments yield singlet exciton diffusion constants of (2 ± 1) × 10^-4cm²s^-1 at 4.2 K and roughly 10^-5 cm² s^-1 at 300 K. The exciton trapping radii can be estimated to be of the order of 60 Å for A and 10 Å for 2-MN. At temperatures below 40 K a partially coherent exciton motion can be inferred, above 40 K the exciton motion appears to be purely incoherent.     

Hemoglobin-catalyzed fluorometric method for the determination of glutathione

A new spectrofluorometric method for the determination of glutathione based on the reaction catalyzed by hemoglobin was reported. The reaction product gave a highly fluorescent intensity with the excitation and emission wavelengths of 320.0 nm and 413.0 nm, respectively. The optimum experimental conditions were investigated. Results showed that low concentration glutathione enhanced the fluorescence intensity significantly. The line ranges were 1.0 × 10^–6–1.0 × 10^–5 mol L^–1 of glutathione and 6.0 × 10^-10 mol L^-1–1.0 × 10^-8 mol L^-1, respectively. The detection limit was calculated to be 1.1 × 10^-11 mol L^-1. The recovery test by the standard addition method gave values in the range of 90.78%-102.20%. This method was used for the determination of glutathione in synthetic and real samples with satisfactory results.     

一种测定某些离子导体的导电基本参数的新方法

利用低频交变电场在某些离子导体中能引起偏振态改变的光衍射特性,发展了一种测量这些离子导体的导电基本参数的新方法,并且用它测定了α-LiIO₃单晶的基本离子导电参数,测得其载流子的迁移率激活能E_μ=0.36eV;夫仑克耳缺陷的形成能为E_M=0.59eV;300K时正、负载流子的数密度均为1.6×10¹⁷cm^-3,相对浓度均为1.07×10^-5;当所加电场反平行于晶体的自发极化强 关键词：     

准2-2型磁电多层复合材料的磁电性能

用带底座的Pb（Zr,Ti）O₃薄片阵列作为压电相,Terfenol-D粉末与树脂的混合物作为磁致伸缩相,灌注复合得到准2-2型磁电多层三相复合材料.研究了这种准2-2型多层结构在不同偏置磁场和不同角度下的磁电效应.其面内相互垂直的两个方向磁电电压系数分别在0.15和0.225 T磁场下达到峰值,低频下分别为1.62×10⁵ V·m^-1T^-1和1.75×10⁵ V·m^-1T^-1;而在垂直于面内方向,低频下磁电系数仅有1.3×10⁴ V·m^-1T^-1,体现出显著的磁电各向异性.这种准2-2型磁电多层复合材料具有较好的交流磁场灵敏度,在谐振频率下可以探测到10^-9 T的交流磁场的变化.进行合适的设计和排列,可以探测空间磁场的大小和方向,有望应用于磁场传感器等领域. 关键词： 磁电效应 多铁性 多层复合材料     

Application of photothermal deflection spectroscopy for the determination of iron(II) with ferrozine with sorption preconcentration on Silufol

Photothermal deflection spectroscopy was applied for selective detection of the intensely coloured iron(II) chelate with ferrozine on Silufol plates. The linearity range was 1×10^-11 - 6×10^-8 mol cm^-2 of chelate at the plate surface, which corresponded to 1×10^-9 - 4×10^-6 M of chelate in solution. The limits of detection and quantification are 8×10^-12 and 20×10^-12 mol cm^-2 at the plate from 15 μL of test solution (0.5 nM and 1.5 nM in solution, respectively), which corresponded to n ×10^-18 mol absolute amounts of the chelate at the detection zone.     

基于沉淀工艺制作四脚氧化锌纳米材料场致发射阴极的研究

采用沉淀法制备四脚氧化锌纳米材料场致发射阴极,将阴极和荧光屏封装起来抽真空并对屏施加电压,测试阴极的发射电流和荧光屏的发光亮度.利用沉淀法制备出面积为(13×15) cm²的阴极,测试结果表明,硅酸钾体积百分比在50×10^-3—83×10^-3范围,硝酸钡浓度在50×10^-4—77×10^-4 M范围,四脚氧化锌的浓度在82×10^-4—12×10^{-3关键词： 场致发射 沉淀法 显示屏亮度}     

Recrystallization behavior of high-dose Mn+-implanted GaAs

Raman spectroscopy was used to study the evolution of host lattice recrystallization in Mn⁺-implanted GaAs. A high dose of Mn⁺-ions (>10¹⁵ cm^-2) was introduced into semi-insulating GaAs by the combinatorial implantation method. Subsequent thermal annealing at 920 °C was carried out to re-grow the implantation-induced amorphous layers. The dependence of the recrystallization behavior on the Mn content was systematically observed. The lattice orientation of recrystallized layers in the surface changed after high-dose implantation (>1.6×10¹⁵ cm^-2) and annealing. The size of the recrystallized crystallites decreased with increasing Mn⁺ dose, as indicated by images from atomic force microscopy. The decrease in the phonon frequency of the Raman lines with the size reduction of microcrystals was in good agreement with the spatial correlation model. However, at higher doses (>7×10¹⁶ cm^-2), a blue shift of the frequency was observed due to the compressive stress exerted on the microcrystals. Received: 5 March 2002 / Accepted: 29 August 2002 / Published online: 8 January 2003 RID="*" ID="*"Corresponding author. Fax: +86-21/658-30734, E-mail: jqwang@mail.sitp.ac.cn     

Er3+在二氧化硅介孔分子筛中的高效率发光及其分析

研究了一种新型的负载Er³⁺的二氧化硅介孔分子筛纳米材料,分析了其在有无功能化试剂全氟甲基磺酰(bis(perfluoromethylsulfonyl)amine)修饰作用下的吸收和荧光光谱特性,获得了高强度的荧光发射. 应用Judd-Ofelt理论计算了强度参数(Ω₂＝1.88×10^-20cm²,Ω₄＝5.45×10^-20cm^{2关键词： 发光 二氧化硅介孔分子筛 稀土离子 Judd-Ofelt理论}     

深圳城市气溶胶物理光学特性的观测研究

气溶胶是影响气候变化和空气污染的重要因子.在深圳地区展开气溶胶观测实验,可以获得可靠的光学物理特征,进而有助于准确评估气溶胶在新型超极城市区域的气像和环境效应.本文利用2010年12月至2011年8月太阳光度计、黑碳和浊度计等气溶胶观测资料,分析了新型超级城市深圳地区的气溶胶物理光学特性.深圳地区气溶胶呈明显季节变化,冬、春季由于城市污染性气溶胶的影响,气溶胶光学厚度和Angstrom波长指数都较大,夏季受海盐气溶胶的影响,光学厚度较小,Angstrom波长指数也较小.光学厚度与Angstrom 波长指数对比表明城市综合性污染是引起深圳气溶胶高光学厚度的主要原因.深圳地区气溶胶的散射系数、吸收系数的平均值(标准偏差)分别为178.7×10^-6 m^-1(126.6×10^-6 m^-1)和32.5×10^-6 m^-1(18.1×10^-6 m^-1),均低于珠三角腹地多年观测平均值的二分之一和国内其他大型城市观测值.而单次散射反照率为0.81,与珠三角其他地区得到的结果接近.此外,气溶胶吸收、散射和单次散射反照率呈明显日变化,可能主要受大气边界层变化的影响.     

V:YAG – a new passive Q-switch for diode-pumped solid-state lasers

gsa =3.0×10^-18 cm² and σ_esa=1.4×10^-19 cm² at 1064 nm, and σ_gsa=7.2×10^-18 cm² and σ_esa=7.4×10^-19 cm² at 1342 nm. Q-switched operation was demonstrated at 1064 nm and 1342 nm from a Nd:YVO₄ microchip laser, producing pulses as short as 9.3 ns at 1342 nm with peak powers of 350 W. Received: 17 March 1998/Revised version: 8 June 1998     

Initial oxidation of Al films investigated by AES,work function and gravimetric measurements

The beginning oxidation of evaporated Al films was measured under UHV conditions by means of AES, gravimetric oxygen uptake and work function changes. The high resolution of our quartz oscillator microbalance (Δm = 7 × 10^-11g/cm² with a time response <1 s) allowed to separate two reaction rates, a logarithmic one for an oxygen uptake <6 × 10^-8g/cm² and an inverse-logarithmic one for Δm > 7.5 × 10^-8g/cm². At room temperature a decrease of work function with an equilibrium value of -0.75 eV (oxygen uptake 9.10^-8g/cm²) with increasing oxidation was observed. This is interpreted as incorporation of oxygen and diffusion of Al^δ+ ions to the surface. But at T = 80 K an increase of work function with a maximum value of 0.5 eV was found. This is attributed to adsorbed oxygen because the incorporation is much slower at this temperature. The AES of pure Al is characterized by the low energy 64 eV peak. The decrease of the 64 eV peak and the increase of two new peaks at 50 and 37.5 eV during the oxidation were measured as a function of oxygen uptake and attributed to the change of electron density of states in the conduction band of aluminum.     

Microwave to X ray up-conversion by undulated electron beams

The device previously known as “free electron laser” is shown to act in some kinematical conditions as a radiation up-converter and amplifier. Its application to the presently available electron beams allows the production of tunable coherent radiation in the range 10¹⁰–10¹⁹ Hz (10^-4–10^-5 eV).     

Laser emission of (Nd,Y)-pentaphosphate at 1.32 μm

The room-temperature cw lasing of (Nd, Y)-pentaphosphate crystals at an optical wavelength of 1.32 μm is reported. The absorbed pump power at threshold was 12 mW using the 514 nm line of an argon laser as pump source. The cross section for stimulated emission at 1.32 μm was 0.2 x 10^-19 cm² as compared with 1.43 x 10^-19 cm² for emission at 1.052 μm.     

A first study of dielectronic recombination with the super-expanded electron beam in CRYRING

A first temperature measurement of the expanded electron beam from a super-conducting magnet in the cooler of CRYRING is reported. It is based on detection of a dielectronic recombination resonance in C²⁺. For this measurement C³⁺ was stored in the ring at 3 rm{MeV/amu} energy. A fit to the resonance with free transverse and longitudinal temperatures gave 3.9 × 10^-3 eV and 4.5 × 10^-5 eV, respectively. The result is also compatible with the values of 10^-3 eV for the transverse and 6.7 ×10-5 eV for the longitudinal component, in good agreement with expected values. This revised version was published online in July 2006 with corrections to the Cover Date.     

Magnetic monopole search at high altitude with the SLIM experiment

The SLIM experiment was a large array of nuclear track detectors located at the Chacaltaya high altitude Laboratory (5230 m a.s.l.). The detector was in particular sensitive to intermediate mass magnetic monopoles, with masses 10⁵ GeV <M_M< 10¹² GeV. From the analysis of the full detector exposed for more than 4 years a flux upper limit of 1.3×10^-15 cm^-2 s^-1 sr^-1 for downgoing fast intermediate mass monopoles was established at the 90% C.L. PACS 14.80.Hv; 29.40.Wk; 29.90.+r     

Development of fluorescent FeIII sensor based on chalcone

In this paper, 4-dimethylamino 2,5-dihydroxy chalcone (DMADHC), which exhibits excited state intramolecular charge transfer (ICT) characteristics, was synthesized and characterized. A sensitive optochemical sensor for Fe³⁺ ion was developed using DMADHC as fluorescence receptor. The fluorescence of DMADHC was gradually quenched with the addition of Fe³⁺ ion, which attributed to the formation of 1:1 complex between DMADHC and Fe³⁺ ion. The sensor exhibited excellent selectivity for Fe³⁺ ion over a large number of cation ions such as alkali, alkaline earth and transitional metal ions with a linear range of 3.984×10⁻⁷-1.135×10⁻⁵ and a limit of detection of 8.223×10⁻⁸ mol/L. On this basis, the sensor was preliminary applied to the determination of the content of iron ions in multi-vitamin tablet with satisfied results and the recoveries were in the 95-100% interval, and precision (n=5) was better than 5%.