A multiphoton ionization study of acetone using time-of-flight mass spectrometry

The 3p Rydberg states of acetone and photodissociation of the acetone cation were studied using time-of-flight (TOF) mass spectrometry. The 3p Rydberg state spectroscopy of acetone was investigated with linearly polarized two-photon resonance enhanced multiphoton ionization (REMPI) from 320 to 337 nm. Several new transition bands were observed in the spectra. In addition to the CH₃COCH₃ ⁺ ion, CH₃CO⁺ and CH₃ ⁺ fragments were observed. The laser power dependences suggest that the CH₃COCH₃ ⁺, CH₃CO⁺ and CH₃ ⁺ ions are produced in three-, four-, and four-photon processes, respectively. Production of CH₃CO⁺ and CH₃ ⁺involves excitation of the ground state acetone cation by an additional photon and subsequent decomposition of the excited acetone ion. The average translational energies of CH₃CO⁺ and CH₃ ⁺ from dissociation in CH₃COCH₃ ⁺(X) + hv → CH₃CO⁺ + CH₃ and CH₃COCH₃ ⁺(X) + hv → CH₃ ⁺ + CH₃CO, respectively, were derived from the ion TOF peak profiles.     

不同氛围溅射HfO_2栅介质薄膜的电学性能和界面微结构

本文研究了不同沉积氛围(纯Ar,Ar+O2和Ar+N2)中射频磁控溅射制备HfO2薄膜的介电性能和界面微结构.实验结果表明在纯Ar氛围室温制备的HfO2薄膜具有较好的电学性能(有效介电常数ε-r～17.7;平带电压～0.36 V;1 V栅电压下的漏电流密度～4.15×10-3 A cm-2).高分辨透射电子显微镜观测和X射线光电子能谱深度剖析表明,在非晶HfO2薄膜和Si衬底之间生成了非化学配比的HfSixOy和HfSix混合界面层.该界面层的出现降低了薄膜的有效介电常数,而界面层中的电荷捕获陷阱则导致薄膜电容-电压曲线出现顺时针的回线.     

Application of the Mole-8.5 supercomputer: Probing the whole influenza virion at the atomic level

Discrete computer simulations are quite helpful in understanding dynamic structures in complex systems. Recently, using the Mole-8.5 supercomputer and molecular dynamics simulations as a “computational microscope”, we simulated the dynamic structure of a whole H1N1 influenza virion in solution for the first time at the atomic level. In total, 300 million atoms in a periodic cube with an edge length of 148.5 nm were simulated. Using 288 low level hybrids with 1728 C2050 GPUs and a software package developed specifically for the hardware, the simulation executed 770 ps/d with an integration time step of 1 fs, and analyzed the dynamic structure. With the tremendous computational power of GPUs, efficient software packages for various hardware designs, and consistent physical models, more challenging applications will be carried out in the near future.     

不同气氛沉积和后退火处理的HfOx〈2薄膜的弱铁磁性

无磁性掺杂HfO2薄膜的室温弱铁磁性是2004年发现的一种不能用传统固体铁磁理论释的奇特磁现.本文用射频磁控溅射方法在不同气中制备和后退火HfOx薄膜样品,对比研究气对其室温弱铁磁性的影响.物析表明,室温沉积在蓝石衬底上的HfOx薄膜为部晶的单斜多晶薄膜,且存在一定程度的氧失配.室温磁性测量果显示HfOx〈2多晶薄膜具有典型的弱铁磁性磁化曲,且饱和磁矩具有各异性.对比实验果表明,缺氧气（纯氩或氩氮混合气）中沉积薄膜的和磁矩略大于富氧气（氩氧混合气）中沉积薄膜的和磁矩.缺氧气（纯氮和高真空）中后退火处理后,薄膜饱和磁矩随着退火温度的升高而增大;而纯氧气中后退火处理后,薄膜和磁矩大幅减小.沉积和后退火气中氧含量的高低对薄膜和磁矩的显影响表明氧空位是HfOx〈2薄膜弱铁磁性的要来源之一.     

Synthesis of a novel triple-site diphosphinoamine （PNP） ligand and its applications in ethylene tetramerization

A novel triple-site diphosphinoamine （PNP） ligand was synthesized and characterized. In combination with Cr（Ⅲ） and methylaluminoxane （MAO）, it generated active catalytic systems for ethylene tetramerization toward 1-octene with high catalytic activity and long lifetime. The effects of reaction temperature, molar ratio of AI/Cr and molar ratio of ligand/Cr on catalytic activity and selectivity to 1-octene were studied with reaction kinetics of the catalytic system for ethylene tetramerization described. At the AI/Cr molar ratio of 100, the catalytic activity is up to 2.29×10^6 g· mol^-1 （Cr）· h^-1 and the selectivity to 1-octene is 49.65 wt%.     

Flame propagation characteristics and flame structures of zirconium particle cloud in a small-scale chamber

Flame propagating through zirconium particle cloud in a small-scale vertical rectangle chamber was investigated experimentally. In the experiments, the zirconium quoted 99% purity was used and the diameter of particles was distributed 1–22 μm. The zirconium dust was dispersed into the chamber by air flow and ignited by an electrode spark. A high-speed video camera was used to record the images of the propagating flame. Micro-thermocouples, schlieren optical system and microscopic lens were used to obtain temperature profiles and flame structure, respectively. Based on the experimental results, flame propagation characteristics and flame structure of zirconium particle cloud were analyzed. The propagation velocity of the flame is quite slow in the initial 14 ms and then accelerates to maximum value. Subsequently, the propagation velocity of the flame almost keeps constant. The combustion zone width of zirconium particle cloud is 5–6 mm. Smaller particles burn mainly at the leading edge of combustion zone in the width of 1.4 mm followed by larger particles burning 1.4–6 mm behind the leading edge of the combustion zone. Gas phase flame is not seen in zirconium particle cloud and the combustion time of single zirconium particle is 1–5 ms, which depends on its original size. The preheated zone is 7–8 mm thickness ahead of the combustion zone and intensive chemical reaction takes place at 490 K. The maximum flame temperature increases at lower concentrations, reaches the maximum value, and then decreases slightly at higher concentrations.     

Efficient parallel implementation of the lattice Boltzmann method on large clusters of graphic processing units

Many-core processors, such as graphic processing units (GPUs), are promising platforms for intrinsic parallel algorithms such as the lattice Boltzmann method (LBM). Although tremendous speedup has been obtained on a single GPU compared with mainstream CPUs, the performance of the LBM for multiple GPUs has not been studied extensively and systematically. In this article, we carry out LBM simulation on a GPU cluster with many nodes, each having multiple Fermi GPUs. Asynchronous execution with CUDA stream functions, OpenMP and non-blocking MPI communication are incorporated to improve efficiency. The algorithm is tested for two-dimensional Couette flow and the results are in good agreement with the analytical solution. For both the oneand two-dimensional decomposition of space, the algorithm performs well as most of the communication time is hidden. Direct numerical simulation of a two-dimensional gas-solid suspension containing more than one million solid particles and one billion gas lattice cells demonstrates the potential of this algorithm in large-scale engineering applications. The algorithm can be directly extended to the three-dimensional decomposition of space and other modeling methods including explicit grid-based methods.     

Resonance-enhanced multiphoton ionization spectroscopy on the B''''~2Σ~+ and B~2Π states of NS

Resonance-enhanced multiphoton ionization (REMPI) spectra of N32S and N34S have been recorded in the range of 35700―40200 cm?1. The radical was generated by a pulsed dc discharge of a mixture of SF6 and N2 under a supersonic free jet condition. All the 16 observed bands of N32S radicals have been as-signed, among which 12 bands belong to three transition progressions (v'=0-4, 0), (v'=1-4, 1) and (v'=2-4, 2) from the X2Π ground state to the B'2Σ upper state and the rest correspond to (9, 0), (10, 0), (11, 0) and (12, 0) bands of B2Π-X2Π transition, respectively. Analysis of the rotationally resolved spectra yields exhaustive spectroscopic constants of both the X2Π ground state and the B'2Σ excited state. The electronic transition bands of the isotopic molecule N34S have been rotationally analyzed for the first time and the rotational constants of the ground and upper states have been determined simultaneously.     

Microstructure of premixed propane/air flame in the transition from laminar to turbulent combustion

In order to explore the flame structure and propagation behavior of premixed propane/air in the transi-tion from laminar to turbulent combustion, the high speed camera and Schlieren images methods were used to record the photograph of flame propagation process in a semi-vented pipe. Meanwhile, the super-thin thermocouple and ionization current probe methods were applied to detect the temperature distribution and reaction intensity of combustion reaction. The characteristics of propane/air flame propagation and microstructure were analyzed in detail by the experimental results coupled with chemical reaction thermodynamics. In the test, the particular tulip flame behavior and the formation process in the laminar-turbulent transition were disclosed clearly. From the Schlieren images and iron current results, one conclusion can be drawn that the small-scale turbulent combustion also appeared in laminar flame, which made little influence on the flame shape, but increased the flame thickness obviously.     

基于光学遥感数据虹湾地区铁钛含量反演研究

月球表面的铁钛含量分布对月球的起源与演化研究以及月球资源的开发利用都具有重要意义.不同遥感数据获得的铁钛含量常不相同,有必要利用多种遥感数据获得月表铁钛含量,并对反演结果进行对比分析.本文利用Chandrayaan-1搭载的Moon Mineralogy Mapper（M3）两个光学周期（OP1B和OP2C）数据以及＂嫦娥一号＂搭载的干涉成像光谱仪（IIM）两套定标数据（pc1和pc2）反演虹湾地区铁钛含量.结果表明OP1B和OP2C数据反演该地区铁峰值分别为17.80wt%和17.60wt%,高于pc1的15.80wt%及pc2的14.00wt%,铁均值分别为16.91wt%和16.79wt%,高于pc1的14.11wt%及pc2的13.46wt%.OP2C数据获得虹湾地区0wt%-4wt%钛丰度百分含量最高,达74.56%,高于pc1的54.66%及pc2的62.46%,OP1B数据得到的0wt%-4wt%钛丰度百分含量最低,为37.55%.OP1B和OP2C数据反演虹湾地区钛均值分别为5.35wt%和3.16wt%,pc1和pc2数据反演该地区钛均值分别为4.25wt%和3.65wt%.极低钛和低钛玄武岩占虹湾地区玄武岩的比例约为50%和40%,主要分布于雨海纪月海物质（Im1,Im2）地层单元内;高钛玄武岩所占比例约为10%,主要分布于爱拉托逊纪月海物质（EIm）地层单元内.总体来看,遥感数据获得的玄武岩钛含量呈单峰分布,低钛玄武岩占优,与样品钛含量的双峰分布不同.虹湾地区玄武岩铁钛含量,随其年龄越来越年轻,有增加的趋势.pc2数据光度校正效果最好,pc1数据光度校正精度较低,M^3不同光学周期反射率差别较大,光度校正有待改进.