CO2,O2,CF4液体微滴喷射靶激光等离子体光源光谱

基于软X射线辐射计量和极紫外投影光刻(EUVL)应用,研制了一台使用纳秒激光器的液体微滴喷射靶激光等离子体(LPP)极紫外光源。该光源由一个可连续控温的不锈钢电磁喷气阀门、YAG激光器和能同步控制喷气阀门和激光器的脉冲发生器组成。使用液氮作致冷剂,控温范围77～473 K。对于足够高的背景气压和低的阀门温度,当气体经过阀门脉冲式地喷入真空靶室内时,气体经过气-液相变碎裂成大量的液体微滴形成液体微滴喷射靶。首先,依据非相对论量子力学理论,使用原子光谱分析常用的Cowan程序,计算了O2,CO2和CF4等几种液体在1011～1012W.cm-2激光功率密度下可能相应产生的O4 ,O5 ,O6 ,O7 ,F5 ,F6 和F7 离子的电偶极辐射跃迁波长和跃迁概率。其次,在激光焦点功率密度为8×1011W.cm-2时,测量了CO2,O2,CF4液体微滴喷射靶在6～20 nm波段的光谱。理论计算结果与实验结果相比较,得出了所测量谱线的电偶极辐射跃迁波长和跃迁概率以及跃迁能级所应归属的组态和光谱项。     

Effect of the structure of nitroxyl radicals on the kinetics of their acid‐catalyzed disproportionation

Acid‐catalyzed disproportionation of cyclic nitroxyl radicals R₂NO^? includes the half‐reactions of their oxidation to oxoammonium cations R₂NO⁺ and reduction to hydroxylamines R₂NOH. For many nitroxyl radicals, this reaction is characterized by its ~100% reversibility. Quantitative characteristics of acid–base and redox properties of the whole redox triad may be obtained from research of kinetics and equilibrium of this reaction. Here, we have examined the kinetics for the disproportionation of twenty piperidine‐, pyrroline‐, pyrrolidine‐, and imidazoline nitroxyl radicals in aqueous H₂SO₄, and interpreted it in terms of the excess acidity function X. The rate‐limiting step of this reaction is R₂NO^? oxidation by its protonated counterpart R₂NOH^+?. Kinetic stability of R₂NO^? in acidic media depends on the basicity of nitroxyl group. This basicity is influenced predominantly by protonation of another, more basic group in radical structure, and its proximity to nitroxyl group. The discovered estimates of pK values for radical cations R₂NOH^+? (from ?5.8 to ?12.0) indicate a very low basicity of nitroxyl groups in all commonly used R₂NO^?. For the first time, a linear correlation is obtained between the one‐electron reduction potentials of oxoammonium cations and the basicity of nitroxyl groups of related radicals. Copyright © 2013 John Wiley & Sons, Ltd.     

用激光解吸附电离法对三甲苯生成二次有机气溶粒子的分析

利用实验室烟雾腔,在不同的实验条件下研究了由羟基启动的三甲苯光氧化反应所产生的二次有机气溶胶,采用激光解吸附技术和气溶胶飞行时间质谱仪测量了产物的化学组分和粒子的粒径分布。结果表明:随着反应物三甲苯浓度的增加,所生成的二次有机气溶胶粒子数量增多;随着反应时间的延长,生成的粒子数目也增加,但是反应到一段时间后,检测到的粒子数目几乎保持不变;光照强度的增加有利于二次有机气溶胶的生成;通过对产物的化学成分分析,说明了在二次有机光氧化产物中粒子相产物主要是芳香的环保留产物、非芳香环保留产物和环断裂产物。     

Measurement of Inherent Material Density of Nanoparticle Agglomerates

We describe a new technique to measure the size dependent inherent material density of chain agglomerate particles. Measurements were carried out for diesel soot and aluminum/alumina agglomerate particles in the nanometer size range. Transmission electron microscopy was used to measure the volumes of agglomerate particles that were preselected by mass using an aerosol particle mass analyzer. We found that the density of diesel exhaust particles increased from 1.27 to 1.78g/cm³ as particle mobility size increased from 50 to 220nm. When particles are preheated to remove volatile components, the density was 1.77±0.07g/cm³, independent of particle size. The densities measured after heating correspond to the inherent material density of diesel soot. Measurements with aluminum nanoparticles were made downstream of a furnace where aluminum (Al) was converted to alumina (Al₂O₃). From measurements of inherent material density we were able to infer the extent of reaction, which varied with furnace temperature.     

近50年来中国东、西部地面太阳辐射变化及其与大气环境变化的关系

利用1961-2011年中国东、西部地区地面太阳辐射和长期气象数据观测资料, 综合分析了东、西部地区地面太阳总辐射的变化特征, 并结合云量、日照百分率、风速、相对湿度等分析了影响东、西部地面太阳总辐射的变化原因. 结果表明: 近50年来东、西部地区地面太阳总辐射整体呈下降趋势, 下降幅度有所不同; 20世纪90年代之前大部分地区地面太阳总辐射呈下降趋势, 之后呈缓慢增加; 东西部各地区地面太阳总辐射与日照时数间存在显著相关性; 分析影响地面太阳总辐射减少的因素, 东部地区地面太阳总辐射与日照百分率呈显著正相关, 日照百分率是影响地面太阳总辐射减少的主要因素, 总云量与低云量已不是东部地区影响太阳辐射的主要因素; 西部地区地面太阳辐射与云量相关性较低, 主要受大气污染和日照百分率的影响. 风速成为影响地面大气辐射的一个重要因子, 并且风是驱逐大气对流层雾霾等大气污染的主要因子, 这进一步证实了大气污染已经成为影响地面太阳辐射的重要因素, 尤其在中国东部地区.     

基于火星巡视器车载激光诱导击穿光谱仪系统设计米散射激光雷达可行性研究

火星大气气溶胶的地基探测对研究火星大气环境具有重要意义,为了能够在节约火星巡视器/着陆器体积、重量的条件下进行气溶胶探测,论证了基于巡视器车载激光诱导击穿光谱仪系统设计米散射激光雷达方案的可行性。所设计的米散射激光雷达系统使用巡视器车载激光诱导击穿光谱仪的既有硬件资源,加入分光元件和探测器模块,构成与激光诱导击穿光谱仪系统集成的米散射激光雷达,米散射激光雷达与激光诱导击穿光谱仪在火星地表分时工作,互不影响。为了论证所设计的米散射激光雷达的探测性能,对Phoenix火星探测任务中独立的米散射激光雷达得到的一组原始回波信号数据进行了处理,反演得到一组典型火星大气消光系数廓线,结合消光系数廓线与系统硬件参数计算了所设计的米散射激光雷达的回波信噪比,结果表明该系统在所用原始数据被记录的当日在火星大气边界层顶4 km高度处信噪比达到26 dB,在10 km高度附近下降到0 dB,说明基于火星巡视器车载激光诱导击穿光谱仪系统设计米散射激光雷达进行气溶胶探测具有现实可行性。对比Phoenix的独立米散射激光雷达设计方案,基于激光诱导击穿光谱仪的米散射激光雷达不但能够节省巡视器体积、重量,而且发射能量更高,回波接收方案更为简单,数据反演步骤更为简洁。     

确定大气颗粒物平均滞留时间的新方法

从低层大气的基本属性出发,利用大气颗粒物中放射性核素的衰变特性与转移速率等相关信息, 建立了单位体积大气颗粒物中被吸附的放射性粒子数、衰变粒子数和转移粒子数的数学模型, 获得了确定低层大气颗粒物平均滞留时间的新方法.该方法解决了当前相关研究中出现的困惑, 说明了大气具有有限的自净功能,给出了大气颗粒物中同一衰变链上各核素达到活度平衡的条件 及降低平均滞留时间的途径,为大气环境的监测与治理提供了科学依据. 关键词： 大气颗粒物 平均滞留时间 氡子体 监测     

The aerosol penetration through an electret fibrous filter

The aim of this paper is to present a theoretical study of the aerosol penetration through an electret fibrous filter, using a numerical approach. The aerosol sizes considered in this study were in the submicron range, and in the numerical model, the conventional mechanical mechanisms (impaction, interception, diffusion and gravitationally settling) were taken into consideration along with the electrostatic mechanisms, including the Coulombic and dielectrophoretic effects. The aerosol penetration through an electret fibrous filter is heavily dependent on the aerosol penetration of a single fibre. The aerosol penetration through a single electret fibre under various filtration conditions was calculated. The effects of aerosol diameter, aerosol and fibre charge state, face velocity, packing density and aerosol dielectric constant on the aerosol penetration were investigated.     

Laser ablation synthesis of monodispersed magnetic alloy nanoparticles

Monodispersed CoPt alloy nanoparticles were synthesized by a pulsed laser ablation (PLA) technique coupled with a low-pressure operating differential mobility analyzer (LP-DMA). The CoPt alloy nanoparticles were generated by laser ablating a solid Co–Pt target. In CoPt alloy nanoparticles synthesized from a target with a Co composition of 75 at%, the nanoparticle surfaces were covered by an oxide layer and exhibited a core-shell structure. In contrast, no shell was observed in particles generated from a target with a Co:Pt ratio of 50:50 at%. According to an EDX analysis, the compositions of the individual nanoparticles were almost the same as that of the target material. Finally, the magnetic hysteresis loops of the CoPt alloy nanoparticles exhibited ferromagnetism.     

Uncertainties in measured and modelled asymmetry parameters of mineral dust aerosols

The error caused by the uncertainty in the refractive index in the determination of the asymmetry parameter g is studied for a variety of mineral dust aerosol samples at two different optical wavelengths. Lorenz–Mie computations for spherical model particles are compared with results based on laboratory-measured phase functions in conjunction with a commonly used extrapolation method. The difference between the g-value based on measurements and the g-value based on Lorenz–Mie simulations is generally on the same order of magnitude as the error caused by the uncertainty in the refractive index m. For larger effective radii the error in g related to the use of spherical model particles is even larger than that related to the uncertainty in m. This indicates that the use of spherical model particles can be among the major error sources in the determination of the asymmetry parameter of dust aerosols.