Trapping of neutral rubidium with a macroscopic three-phase electric trap

We trap neutral ground-state rubidium atoms in a macroscopic trap based on purely electric fields. For this, three electrostatic field configurations are alternated in a periodic manner. The rubidium is precooled in a magneto-optical trap, transferred into a magnetic trap, and then translated into the electric trap. The electric trap consists of six rod-shaped electrodes in cubic arrangement, giving ample optical access. Up to 10;{5} atoms have been trapped with an initial temperature of around 20 microkelvin in the three-phase electric trap. The observations are in good agreement with detailed numerical simulations.     

The influence of K4Fe（CN）6 on the photosensitivity of cubic AgCl microcrystal

The influence of K4Fe(CN)6 at various doping concentrations on the photosensitivity of cubic AgC1 microcrysgals has been investigated by using the microwave absorption and phase-sensitive measurement technique. The time behaviour of free photoelectrons in AgCl microcrystals is analysed by using computer simulation as a function of three parameters of shallow electron trap (SET) including doping concentration, trap depth and capture cross-section (CCS).It is found that the three parameters of SET play different roles on the free photoelectron decay time (FDT). After considering the threshold effects of the three parameters and their collective effects, the trap depth value, the CCS value,and the optimal doping concentration of the SET introduced by the dopant K4Fe(CN)6 in cubic AgCl microcrystals can also be determined, and the best photosensitivity of cubic AgCl can be obtained.     

分子束外延高Mg掺杂GaN的发光特性

采用分子束外延技术在蓝宝石衬底上制备Ｍｇ掺杂的立方相ｐ－ＧａＮ,并对其不同温度下的光致发光光谱进行了研究．实验观察到高Ｍｇ掺杂ＧａＮ中施主受主对发光的反常温度行为．理论分析表明,高Ｍｇ掺杂ＧａＮ中施主受主对的发光受到陷阱与受主间竞争俘获非平衡空穴过程和空穴隧穿输运过程的影响．     

The thermoluminescence properties of CdS films under nitrogen atmosphere

Chemically deposited cadmium sulphide (CdS) films have been grown on glass at 60 °C and annealed at nitrogen atmosphere at different temperatures. The as-deposited film shows a mix phase of cubic and hexagonal. Once the film subjected to annealing the hexagonal phase becomes dominant and the crystal size increases due to these changes optical band gap energy decreases from 2.44 to 2.28 eV. The electrical conductivity increases depending on temperature and the film annealed at 423 K shows the highest conductivity. Thermoluminescence (TL) intensity of the films was measured after irradiating the films with ⁹⁰Sr/⁹⁰Y β-source and the trap depths were calculated after the TL curves deconvoluted by using the computer glow curve deconvolution (CGCD) method. It is observed that the as-deposited film has three different trap depths, at around 0.257, 0.372, and 0.752 eV corresponding to 383, 473, and 608 K, respectively.     

细胞光阱刚度与折射率关系理论计算

为了探讨用光镊技术进行细胞折射率的测量方法,用几何光线理论对可作为米氏粒子模型的生物细胞(半径a=10μm,折射率n=1.35~1.70),在单光束梯度力光阱[激光波长λ=780 nm,功率P=6 mW,焦斑半径w(0)=0.6μm、0.8μm和1.0μm]中的轴向光阱刚度与细胞折射率关系进行了数值计算。结果表明,光阱刚度随折射率的变化关系与三次多项式曲线拟合得较好;用测量光阱刚度计算细胞的折射率时,需要用折射率已知的四种标准粒子对三次多项式曲线进行标定。     

Dependence of the Bose-Condensate Population Fluctuations in a Gas of Interacting Particles on the System Size: Numerical Analysis

Radiophysics and Quantum Electronics - We consider the Bose-condensate population statistics for a gas of interacting particles confined into a three-dimensional cubic trap with different boundary...     

Cubic algebra and averaged Hamiltonian for the resonance 3: (?1) Penning-ioffe trap

For the 3: (?1) resonance Penning trap, we describe the algebra of symmetries which turns out to be a non-Lie algebra with cubic commutation relations. The irreducible representations and coherent states of this algebra are constructed explicitly. The perturbing inhomogeneous magnetic field of Ioffe type, after double quantum averaging, generates an effective Hamiltonian of the trap. In the irreducible representation, this Hamiltonian becomes a second-order ordinary differential operator of the Heun type.     

Microstrain sensitivity of orbital and electronic phase separation in SrCrO3

An orbital ordering transition and electronic phase coexistence have been discovered in SrCrO3. This cubic, orbitally-degenerate perovskite transforms to a tetragonal phase with partial orbital order. The tetragonal phase is antiferromagnetic below 35-40 K, whereas the cubic phase remains paramagnetic at low temperatures. The orbital ordering temperature (35-70 K) and coexistence of the two electronic phases are very sensitive to lattice strain. X-ray measurements show a preferential conversion of the most strained regions in the cubic phase. This reveals that small fluctuations in microstrain are sufficient to drive long range separation of competing electronic phases even in undoped cubic oxides.     

Antimatter plasmas in a multipole trap for antihydrogen

We have demonstrated storage of plasmas of the charged constituents of the antihydrogen atom, antiprotons and positrons, in a Penning trap surrounded by a minimum-B magnetic trap designed for holding neutral antiatoms. The neutral trap comprises a superconducting octupole and two superconducting, solenoidal mirror coils. We have measured the storage lifetimes of antiproton and positron plasmas in the combined Penning-neutral trap, and compared these to lifetimes without the neutral trap fields. The magnetic well depth was 0.6 T, deep enough to trap ground state antihydrogen atoms of up to about 0.4 K in temperature. We have demonstrated that both particle species can be stored for times long enough to permit antihydrogen production and trapping studies.     

GdVO4:Eu3+的热释光研究

GdVO4:Eu^3 有着十分优良的发光特性，它发光强度高，特别是具有很好的温度特性，在室温以上发光强度随温度的升高而增强，很利于在高温下使用此材料。本文对它的热释光进行了研究，其热释光峰值分别位于193，235和304K，根据计算可知它们的陷阱深度分别为0.39,0.47和0.61eV，陷阱的主要来源可能是F^ ,F和钒空位；Eu^3 掺入导致的晶格畸变，其中最主要的来源可能是空位导致的。     

Single crystal and powder EPR study of trivalent gadolinium in Cs2NaBiCl6 in the 30-300 K interval

A crystalline electric field cubic symmetry site has been reported for Gd³⁺ in Cs₂NaBiCl₆ at room temperature. This host exhibits an apparent structural transformation below 100 K that is completely reversible. However, an EPR examination for a powdered sample of Cs₂NaBiCl₆:Gd³⁺ clearly demonstrates that there are no new large crystalline electric field symmetry sites arising between the transition temperature (100 K) and 30 K, suggesting, therefore, that the site symmetry remains predominantly cubic even at temperatures close to 30 K. In order to substantiate this statement, a computer EPR powder simulation was performed using the single-crystal-spin-Hamiltonian parameters obtained from the three different sites that emerge from the original site while observed at 30 K. A remarkable agreement is observed while comparing the computer-simulated data with that of powdered experimental data. It is important to mention here that several attempts were done trying to fit the observed new spectra to lower crystalline field symmetries, however, our best analytical adjustment was obtained with the cubic spin-Hamiltonian.Below 30 K, new structural transitions are present and the lattice loses its original cubic nature. However, at 10 K the EPR spectrum of the crystal again shows only seven lines that are very broad. This new spectrum cannot be fitted with previously used cubic spin-Hamiltonian parameters.     

A study of the dark currents of InSb charge injection devices

The dark currents of InSb metal-insulator-semiconductor (MIS) charge injection devices (CIDs) in the temperature range 30 to 120K are studied. It is found that a thermal-generating process dominates the dark current in the high temperature region. When the device is under small bias voltage, a bump in the trap emission current appears below 70K. This current is due to carrier capture and emission processes of a hole trap state located in the bulk material, and the measured activation energy is 50meV. For larger bias conditions, the band-to-band tunnelling current gradually overcomes the trap emission current. It smears out the bump in the trap emission current, and shows a slightly temperature-dependent behaviour in the plot. The effects of field electrodes are also studied. It is found from experimental results that the edge of the electric field around the device periphery plays an important role in the band-to-band tunnelling process, and a field electrode with suitable bias can improve the dark current response drastically.     

Subpicosecond pulse generation in synchronously pumped energy transfer dye lasers

We describe a laser-cooling experiment on Mg⁺ ions confined in an electromagnetic trap (Penning trap or rf trap) and give the preliminary experimental results. In particular, we have observed a laser cooling in the Penning trap configuration in which a measured temperature of about 1 K has been obtained.     

甲酸根离子均匀掺杂的卤化银中的光电子特性

甲酸根离子(HCO-2)作为一种“空穴-电子转换剂”掺杂在卤化银中,可以提高潜影形成过程中光电子的利用率,俘获光生空穴,减少潜影形成过程中电子-空穴复合所造成的电子损失;同时还可以释放一个电子,提高感光效率。采用微波吸收介电谱检测技术,检测了不同浓度甲酸根离子均匀掺杂的立方体AgCl和AgBr乳剂在脉冲激光作用下所产生的光电子衰减信号。通过比较光电子的衰减时间和寿命,分析了甲酸根离子的空穴陷阱效应对立方体AgCl和AgBr乳剂中光电子衰减行为的影响,并得到了最佳均匀掺杂浓度（10^-5mol/molAg）。     

The Urbach rule in ZnS crystals

The slope parameters of the exponential absorption edges of 3C cubic, 4H polytypic and 2H hexagonal ZnS crystals were measured as a function of temperature. Their behavior show that different phonons interact with the electron transitions in different temperature ranges, an LA piezoelectric phonon below approximately 100°K and an LO phonon above this temperature up to 300°K. In cubic ZnS the slope parameter was measured up to 750°K and the same LO phonon was found to be involved at these temperatures.     

Realization of a single-beam mini magneto-optical trap: A candidate for compact CPT cold atom-clocks

We have demonstrated the experimental realization of a single-beam mini magneto-optical trap of ⁸⁷Rb atoms, originally designed for a cold atom-clock with coherent population trapping (CPT). Only one beam is used as cooling, trapping and repumping beams rather than the three pairs of orthogonal beams of the standard magneto-optical trap. The core optics, which consists of a modified pyramidal funnel type mirror, a quarter-wave plate and a retroreflect mirror, is installed inside a mini titanium cubic chamber. The vacuum system, rubidium source, magnetic field coils and beam expander are designed in a compact geometry. As many as 1.1 × 10⁷ rubidium atoms are cooled and trapped, and thus the mini trap is ready for the implementation of a novel compact coherent population trapping cold atom-clock.     

Role of remote Coulomb scattering on the hole mobility at cryogenic temperatures in SOI p-MOSFETs

The impacts of remote Coulomb scattering(RCS)on hole mobility in ultra-thin body silicon-on-insulator(UTB SOI)p-MOSFETs at cryogenic temperatures are investigated.The physical models including phonon scattering,surface roughness scattering,and remote Coulomb scatterings are considered,and the results are verified by the experimental results at different temperatures for both bulk(from 300 K to 30 K)and UTB SOI(300 K and 25 K)p-MOSFETs.The impacts of the interfacial trap charges at both front and bottom interfaces on the hole mobility are mainly evaluated for the UTB SOI p-MOSFETs at liquid helium temperature(4.2 K).The results reveal that as the temperature decreases,the RCS due to the interfacial trap charges plays an important role in the hole mobility.     

不同增感对AgCl乳剂中光电子时间行为的影响

借助微波吸收介电谱检测技术,对AgCl立方体乳剂中光电子的时间行为进行了检测,同时获得了自由光电子与浅束缚光电子在不同增感条件下的时间分辨谱。实验结果表明：化学增感时由于硫加金增感中心的浅电子陷阱作用有效地抑制了空穴与光电子之间的复合,化学增感使得光电子的衰减相对未增感的减缓、衰减时间得到延长;光谱增感时由于染料J聚集体增加了卤化银晶体中添隙银离子的浓度、促进了光电子与添隙银离子之间的结合,光谱增感使得光电子的衰减相对未增感的加剧、衰减时间变短;化学与光谱共同增感使光电子的衰减时间在光谱增感的基础上得到了延长,且硫加金化学增感中心的浅电子陷阱效应在光谱增感的基础上更明显。     

Giant optical nonlinearity of an atomic Bose-Einstein condensate and low-threshold bistability

The polarization of an atomic Bose-Einstein condensate weakly excited by laser radiation at a nearly resonance frequency is determined. The coefficient of nonlinearity (cubic in field) in the refractive index of the condensate is calculated for the slow decay mode due to the spontaneous emission of excited atoms, as well as for the stationary mode, when the loss of atoms is compensated by the injection of atoms into the trap. In both cases, the cubic nonlinearity coefficients of the condensate are several orders of magnitude larger than the corresponding values for known nonlinear media. The conditions for observing hysteresis in an interferometer containing the condensate in the stationary state in the presence of an incident laser beam are specified.     

Anomalies in the specific heat of PbF2

We have measured the heat capacity, C_p, of PbF₂ between 400 K and 800 K using a cubic, fluorite-structure, crystal as well as material recovered in the orthorhombic form at room temperature after a fluorite-structure crystal had been pressurized to 4.5 kbar. C_p of each behaved normally up to somewhat above 600 K. However C_p of the recovered material revealed that orthorhombic PbF₂ undergoes a sharp, endothermic, nonreversible transition at T = 633 K, which seems to be a transformation back to the cubic fluorite structure. The C_p of each sample exhibited a λ-like anomaly in the temperature range where a transition to the superionic state is known to occur in cubic PbF₂, thus confirming the second order nature suggested for the transition.