Chemical Synthesis and Characterization of Flaky h-BCN at High Pressure and High Temperature

Hexagonal boron carbonitrogen （h-BCN） compound is synthesized from a mixture of boron powder and CNH compound prepared by pyrolysis of melamine （CaH6N6） under high temperature （1400-1500℃） and high pressure （5.0-5.5 GPa）. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spec- troscopy are used to determine the chemical composition and bonds of the product. The results show that the product has composition of B0.18C0.64N0.16 （near BC4N） and atomic-level hybrid. X-ray diffraction analysis indicates that the powder has a hexagonal network structure. Scanning and transmission electron microscopy results suggest that h-BCN compound morphology is mainly flaky in width about 1 μm and thickness 200nm.     

Structural Investigation of Solid Methane at High Pressure

High pressure studies of solid methane are performed using both classical simulated annealing and first-principles methods. A series of simulated annealing and geometry optimization reveal a monoclinic P21/b structure with the unit cell containing four methane molecules. The phonon dispersion curves and vibrational density of states indicate that this structure is stable in the pressure range 10-90 GPa. The electronic band structure and density of states show that this structure has not metalized until 90 GPa.     

High resolution photoabsorption spectroscopy at the carbonK-Edge

Using plane grating, ellipsoidal mirror, grazing incidence monochromators at the storage ring BESSY, a resolution of 150meV was achieved for a photon energy of 285 eV. This high energy resolution considerably extends the range of possible studies using core level Spectroscopy. Some of the new opportunities are illustrated at the CK edge by resolving the vibrational fine structure of condensed C₂H₄ multilayers in the (1s^–1, ^*) state by means of photoabsorption spectroscopy. For the sake of comparison with other high resolution instruments, the vibrational fine structure of condensed N₂ multilayers at the NK edge ( 400eV) was also measured, yielding a resolving power of 3000.     

Hetero-Epitaxial Diamond Single Crystal Growth on Surface of cBN Single Crystals at High Pressure and High Temperature

We report a new diamond synthesis process in which cubic boron nitride single crystals are used as seeds, FesoNi20 alloy powder is used as catalyst/solvent and natural flake-like graphite is used as the carbon source. The samples are investigated using laser Raman spectra and x-ray diffraction （XRD）. Morphology of the sample is observed by a scanning electron microscope （SEM）. Based on the measurement results, we conclude that diamond single crystals have grown on the cBN crystal seeds under the conditions of high temperature 1230℃ and high pressure 4.8 GPa. This work provides an original method for synthesis of high quality hereto-semiconductor with cBN and diamond single crystals, and paves the way for future development.     

Electrostatic Instabilities at High Frequency in a Plasma Shock Front

New electrostatic instabilities in the plasma shock front are reported. These instabilities are driven by the electro- static field which is caused by charge separation and the parameter gradients in a plasma shock front. The linear analysis to the high frequency branch of electrostatic instabilities has been carried out and the dispersion relations are obtained numerically. There are unstable disturbing waves in both the parallel and perpendicular directions of shock propagation. The real frequencies of both unstable waves are similar to the electron electrostatic wave, and the unstable growth rate in the parallel direction is much greater than the one in the perpendicular direction. The dependence of growth rates on the electric field and parameter gradients is also presented.     

Neutrino Mean Free Path in Strange Matter at High Temperatures

We investigate the condition that the neutrino energies E_v can be considered to be small enough to be neglected in the energy momentum conservation equation in the reactions d+v_e → u+e^- and u+e^- → d+v_e. It can be simply expressed as E_v < 4α_cμ_e/π, where α_c is the strong coupling constant and μ_e is the electron chemical potential. Then for E_v < 4α_cμ_e/π, we generalize the mean free path for nondegenerate neutrinos given by Iwamoto and obtain a formula that is valid for both nondegenerate and degenerate neutrinos. We also model the mean free path for both nondegenerate and degenerate neutrinos with energies E_v < 4α_cμ_e/π.     

Elastic Properties of Rutile TiO2 at High Temperature

Dependence of elastic properties on temperature for rutile TiO2 is investigated by the Cambridge Serial Total Energy Package （CASTEP） program in the frame of density function theory （DFT） and the quasi-harmonic Debye model The six independent elastlc constants of rutile TiO2 at high temperature are theoretically obtained for the first time. It is found that with increasing temperature, the elastic constants will decrease monotonically. Moreover, we successfully obtain the polycrystalline moduli BH and GH, as well as the Debye temperature ⊙D.     

Reshock Response of 2A12 Aluminum Alloy at High Pressures

By means of mounting the specimen on a low-impedance buffer, reshock experiments were carried out on a 2A12 almninum alloy up to shock stresses＇ of 67.6 GPa. Reshock wave profiles from the initial shock stresses of 60.9-67.6 GPa were measured with a velocity interferometer, and it shows that the 2A12 aluminum alloy characterizes as quasi-elastic response during recompression process. The Lagrange longitudinal velocities along the reloading path from initial shock state were obtained from two shots of experiments, while the bulk velocities at corresponding shock stresses were determined via extrapolating from the public reported unloading plastic sound velocities. Combining the reshock and the release experimental results, the yield strength of 2A12 aluminum alloy at shock stress of 60.9 GPa was estimated to be about 1.7GPa.     

A Simple System to Measure Superconducting Transition Temperature at High Pressure

A simple hydride system is fabricated to measure the superconducting transition temperature 1c unaer hign pressure using a diamond anvil cell （DAC）. The system is designed with centrosymetric coils around the diamond that makes it easy to keep balance between the pick-up coil and the inductance coil, while the superconducting states can be modulated with a low-frequency small external magnetic field. Using the device we successfully obtain the Tc evolution as a function of applied pressure up to 10 GPa for YBa2 Cu3 O6＋δ superconductor single crystal.     

Effects of NaN3 Added in Fe-C System on Inclusion and Impurity of Diamond Synthesized at High Pressure and High Temperature

Effects of NaN3 added in Fe-C system to synthesize nitric diamond at high pressure and high temperature are investigated. Diamond crystals with high nitrogen concentration are synthesized by the system of Fe-C and NaN3 additive at pressure 5.8 GPa and at temperatures 1750-1780 K for 15 min. The synthetic diamond crystals have a cubo-octahedral or octahedral shape with yellowish green or green colour. Some disfigurements are observed on the surfaces of most diamond crystals. The composition and content of inclusions formed by iron in diamond are changed and iron nitride is detected in diamond crystals synthesized with Fe-C-NaN3 additive. As the amount of NaN3 additive increases, Fe3C decreases and iron nitride increases with α-Fe being nearly constant. Moreover, the nitrogen concentrations in diamond crystals synthesized with 1.5 wt% NaN3 additive is up to 2250ppm in substitutional form.     

Compact Single-Stage Femtosecond Multipass Ti：Sapphire Amplifier at 1 kHz with High Beam Quality

A compact femtosecond Ti：sapphire amplifier system is reported using single-stage multipass configuration with high beam quality. A high dispersion glass stretcher and a pair of double prisms for compression are introduced based on broadband femtosecond seed pulses. The non-grating-based pulse stretcher and compressor are advantageous to increase high beam quality and to reduce the high-order dispersion. A Gaussian filter is used to reduce the gain narrowing effect in amplification. The compact femtosecond Ti：sapphire nine-pass amplifier delivers pulses with a duration of 26 fs and an energy of 800μJ at 7mJ pumping pulses energy at I kHz. The 1-kHz femtosecond amplifier with high beam quality and high stability is very suitable for ultrafast physics research applications, such as attosecond science, ultra-precision micromachining, and THz wave generation.     

高温高压下干酪根在水中变化的拉曼光谱原位分析

金刚石作为顶砧 ,通过顶砧压腔装置对干酪根在水中的变化进行拉曼光谱的原位分析 ,压力采用常温常压下石英 4 6 4cm-1的拉曼峰确定。在 2 4 0℃之前 ,可得到水、干酪根以及石英清晰的拉曼峰 ,之后 ,由于金刚石的荧光效应 ,使拉曼信号消失。实验中发现 ,温度从最高温度 4 40℃降到 2 4 0℃ ,拉曼光谱图显示干酪根降解生成了有机小分子     

高温高压下电解质溶液谱学研究的进展

高温高压下电解质溶液研究在理论和工业应用上都具有重要的意义，拉曼光谱、红外光谱、紫外可见光谱、中子和X射线衍射、以及X射线吸收精细结构方法都已经用于它的研究。随着温度升高，溶液的结构发生了变化，离子的缔合度增加，内层配位水的数目减少，出现了离子的多核簇组成。除了静态结构的研究外，也用拉曼光谱进行溶液的动力学探讨。水热金刚石压腔装置是高温高压电解质溶液研究的一个重要的进步，在水热金刚石压腔装置中，拉曼光谱和X射线吸收精细结构两种方法具有重要的应用潜力。     

High Efficiency of Two Efficient QSDC with Authentication Is at the Cost of Their Security

Two efficient protocols of quantum secure direct communication with authentication [Chin. Phys. Lett. 25 （2008） 2354] were recently proposed by Liu et al. to improve the efficiency of two protocols presented in [Phys. Rev. A 75 （2007） 026301] by four Pauli operations. We show that the high efficiency of the two protocols is at the expense of their security. The authenticator Trent can reach half the secret by a particular attack strategy in the first protocol. In the second protocol, not only Trent but also an eavesdropper outside can elicit half-information about the secret from the public declaration.     

中高能重离子碰撞中的阵发混沌

在量子分子动力学模型计算多重碎裂基础上,应用阶乘矩方法分析了多重碎裂.对¹⁹⁷An(200MeV/u)+¹⁹⁷An碰撞系统进行了计算.发现多重分布有阵发混沌存在.并对临界现象做了初步讨论.     

High Power Continuous-Wave and Acousto-Optic Q-Switched Nd：GdVO4 Laser Operated at 912 nm

We present a high power and efficient operation of the ^4F3/2 → ^4I9/2 transition in Nd：GdVO4 at 912nm. In the cw mode, the maximum output power of 8.6 W is achieved when the incident pump power is 40.3 W, leading to a slope efficiency of 33.3% and an optical-optical efficiency of 21.3%. To the best of our knowledge, this is the highest cw laser power at 912nm obtained with the conventional Nd：GdVO4 crystal. Pulsed operation of 912nm laser has also been realized by inserting a small aeousto-optie （A-O） Q-Switch inside the resonator. As a result, the minimal pulse width of 20ns and the average laser power 1.43 W at the repetition rate of lOkHz are obtained, corresponding to 7.1 kW peak power. We believe that this is the highest laser peak power at 912nm. Furthermore, duration of 65ns has also been acquired when the repetition rate is 100 kHz.     

High Efficient Continuous-Wave Ho：Y/kG Laser Pumped by a Diode-pumped Tm：YLF Laser at Room Temperature

DUAN Xiao-Ming, YAO Bao-Quan, ZHANG Yun-Jun, SONG Cheng-Wei, GAO Jing, JU You-Lun, WANG Yue-Zhu（ National Key Laboratory of Tunable Laser Technology, Harbin Institute of Technology, Harbin 150001）     

TR4终端高性能探测器系统

描述了兰州中能重离子加速器TR4终端装备的高性能探测器系统的结构性能.各类探测器都达到了很好的性能指标.Si多叠层望远镜,Z/△Z～50,△E/E～0.3%.IC+PSD+SPD+CsI(T1)对数密度望远镜,Z/△Z～44.5,△x～1.7mm.棉球面反射镜结构开始时间探测器装置,△t～140Ps.重离子飞行时间谱仪,A/△A～86,Z/△Z～48,△E/E～0.78%,△t～286ps.9单元和36单元CsI(T1)轻粒子小角度关联探测器阵列,Si+CsI(T1)轻粒子望远镜也达到了很好的性能指标.简述了小角度关联等实验结果.     

液氮温区的小型高频信号检测系统

研究了高温超导约瑟夫逊结的高频信号辐照响应;建立了简便的小型液氮制冷设备,提供79K的工作温度;研究了GPIB仪器控制技术,编写了数据采集软件,利用带有GPIB接口卡的个人电脑以及两个型号为HP34401A的惠普数字多用表,建成一个自动化快速测量系统;利用自动化测量系统测量并研究了高温超导约瑟夫逊结在79K下的直流电流-电压特性曲线以及98GHz高频信号辐照的电压响应和相应的频谱特性。     

Skyrmions at High Density

The phase diagram of quantum chromodynamics is conjectured to have a rich structure containing at least three forms of matter: hadronic nuclear matter, quarkyonic matter and quark gluon plasma. We describe its formulation in terms of Skyrme crystals and justify the origin of the quarkyonic phase transition in a chiral-quark model.