平均原子模型中谱线位置偏移对辐射不透明度的影响

使用平均原子(average atom,AA)模型计算了局域热动平衡近似下的Fe,Br等离子体的辐射不透明度.对AA模型中跃迁系的跃迁能量引入了统计修正，修正后的谱线位置与细致谱项模型的结果更接近，但仍然存在差距，进一步减小这种差距需要考虑等离子体的价态分布.研究了AA模型中这种谱线位置移动对平均不透明度的影响，计算了Fe等离子体等温度系列的平均不透明度，发现这种修正对于平均不透明度的影响是比较明显的.     

Radiative properties of matter based on quantum statistical method

We present the preliminary results of our code OPAQS(opacity calculation using quantum statistical model) that is based on the self consistent Hartree-Fock-Slater model for the average atom. The code is capable of performing robust calculations of average charge state, frequency-dependent and mean opacities. The accuracy of the atomic model is verified by comparing the calculations of average charge state with various published results. The monochromatic opacities for iron computed at different sets of temperatures and densities are compared with LEDCOP. The Rosseland and Planck opacities for iron and aluminum are validated with some state-of-the-art codes. The results are in good agreement with the published data.     

Charge-state distribution and Doppler effect in an expanding photoionized plasma

The charge state distributions of Fe, Na, and F are determined in a photoionized laboratory plasma using high resolution x-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter xi=20-25 erg cm s(-1) under near steady-state conditions. Line opacities are well fitted by a curve-of-growth analysis which includes the effects of velocity gradients in a one-dimensional expanding plasma. First comparisons of the measured charge state distributions with x-ray photoionization models show reasonable agreement.     

Synthesis of nanoparticles in an atmospheric pressure glow discharge

Nanopowders are produced in a low temperature, non-equilibrium plasma jet (APPJ), which produces a glow discharge at atmospheric pressure, for the first time. Amorphous carbon and iron nanoparticles have been synthesized from Acetylene and Ferrocene/H₂, respectively. High generation rates are achieved from the glow discharge at near-ambient temperature (40–80°C), and rise with increasing plasma power and precursor concentration. Fairly narrow particle size distributions are measured with a differential mobility analyzer (DMA) and an aerosol electrometer (AEM), and are centered around 30–35 nm for carbon and 20–25 nm for iron. Particle characteristics analyzed by TEM and EDX reveal amorphous carbon and iron nanoparticles. The Fe particles are highly oxidized on exposure to air. Comparison of the mobility and micrograph diameters reveal that the particles are hardly agglomerated or unagglomerated. This is ascribed to the unipolar charge on particles in the plasma. The generated particle distributions are examined as a function of process parameters.     

Self-organized transformation to polyaniline nanowires by pulsed energetic electron irradiation in a plasma focus device

An ingenious method for fabricating network of polyaniline nanowires at room temperature in microsecond timescale is demonstrated by using the pulsed electron beam of a plasma focus device. The electron beam of the plasma focus device having a wide range of energies (10-200 keV) was irradiated on to the freestanding polyaniline film. The growth of polyaniline nanowires on the surface of film sample is confirmed by field emission scanning electron microscope images showing nanowires of about 50-80 nm in diameter and up to few tens of micrometers in length.     

Characterization of ultrafine zirconia and iron oxide powders prepared under hydrothermal conditions

Abstract

Nanocrystalline zirconia (6-20 nm) and iron oxide (20-80 nm) powders were produced by hydrothermal treatment of corresponding hydroxides and nitrate solutions. The synthesis parameters (temperature, duration, concentration) allow fabrication of ultrafine oxide powders with various particle size and morphology. The smallest particles were produced by short-time (4-7 s) treatment of nitrate solutions (PH ≈ 1). Prepared nanocrystalline powders exhibit high activity in model solid state reactions.     

Optical Emission Studies of Molybdenum Plasma Produced by an Nd:yag Laser

We study the optical emission characteristics of a molybdenum (Mo) plasma produced at the surface of a target material in air at atmospheric pressure using the fundamental (1,064 nm) wavelength of an Nd: YAG laser. We estimate the temperature using the Boltzmann plot method, whereas the number density is calculated using the Stark broadening profile of the neutral iron (Fe I) transition line at 538.34 nm. We investigate variations in the temperature and number density at different laser irradiance as well as the distance from the target surface along the axial direction of plasma propagation using the spectroscopic technique. We observe that the temperature and number density increase with increase in the laser irradiance.     

Stable generation of high-order harmonics of femtosecond laser radiation from laser produced plasma plumes at 1 kHz pulse repetition rate

We present a method for the creation of stable weakly ionized plasmas from laser ablation of solid targets using a 1 kHz pulse repetition rate laser, which can be used for stable high-order harmonic generation from plasma plumes. The plasma plumes were generated from cylindrical rotating targets. Without target rotation the intensity of harmonics in the 40-80 nm range drops by more than one order of magnitude during less than 10(3) shots, while, with rotation of the target at typically 30 revolutions per minute, stable emission of high-order harmonics from aluminum plasma plumes with variation of less than 10% was maintained for >10(6) laser shots.     

纳秒脉冲激光诱导空气等离子体的近红外辐射特性

开展纳秒激光诱导空气等离子体近红外辐射特性的实验研究,对波长为532 nm的脉冲ns激光诱导产生的空气等离子体的近红外光谱进行测量.结果表明:空气等离子体的近红外辐射在光谱范围为1100-2400 nm内由连续谱和线状谱组成,光谱指认表明线谱主要来源于N,O原子的中性原子谱和氮分子的振动光谱.通过对连续谱的分析得知,黑体辐射是连续辐射的主要来源.空气中波长1128 nm附近的辐射,可能是N和O中性原子谱的贡献.保持真空腔内气压不变,改变腔内氮气和氧气气体组分含量,分析测得的红外光谱数据,可知混合气体中氧气和氮气含量变化只对波长为1128 nm附近的辐射有影响.利用二元线性回归分析对数据进行分析后得知,氧气对波长为1128 nm附近的辐射贡献较大.最后从电离难易的角度分析造成这一结果的原因.     

基于LED的非相干宽带腔增强吸收光谱技术

介绍了基于可见光波段高功率LED作为光源的高灵敏度宽带腔增强吸收光谱技术,该系统的探测灵敏度通过测量NO₂在472.3～479.3 nm范围内的吸收得到验证。将中心波长为457 nm的高功率LED发出的宽带非相干光耦合进入92.5 cm长、由两片高反射率透镜组成的高精度光学谐振腔内,使用CCD光谱仪(HR2000)测量透过光学腔的光强信号。腔镜在472.3～479.3 nm波长范围内的反射率通过O₂-O₂聚合物的吸收确定,实验测量了一系列低浓度NO₂气体样品,采用差分光谱拟合技术在80 s的平均时间内NO₂浓度反演的统计不确定性约为3.1 ppb(ng·mL-1)。     

Elemental analysis in environmental land samples by stand-off laser-induced breakdown spectroscopy

The stand-off detection and analysis of environmental land samples have been demonstrated using laser-induced breakdown spectrometry. The samples of interest have included soils and vegetation powder. Elements Hg, As, Pb, Zn, Cd and Cr have been spectrally analysed with a focus on Hg as a trace contaminant in the samples. It is found that element Fe, usually contained in land samples, is a main source of spectral interference for Hg detection due to its ever present iron emission line at 253.68 nm that is closely adjacent to the strongest Hg emission line at 253.65 nm, and hence, a high resolution of spectral detection is necessary. The strong spectral signals from Bremsstrahlung emission in laser-induced plasma and atomic emission of Fe of high concentration caused a significant reduction in detection resolution in the use of image intensifier of an ICCD. The limit of detection at ~8 ppm for Hg detection in soil samples with iron as a minor constituent has been achieved, using an optical chopper and a CCD detector for laser-induced breakdown spectroscopy (LIBS) signal detection. Such detection method in LIBS system has shown a great advantage in determining trace elements from interfering elemental constituents in land sample matrixes.     

Selective growth, characterization, and field emission performance of single-walled and few-walled carbon nanotubes by plasma enhanced chemical vapor deposition

Single-walled carbon nanotubes (SWCNTs) and few-walled carbon nanotubes (FWCNTs) have been selectively synthesized by plasma enhanced chemical vapor deposition at a relative low temperature (550 °C) by tuning the thickness of iron catalyst. The parametric study and the optimization of the nanotube growth were undertaken by varying inductive power, temperature, catalyst thickness, and plasma to substrate distance. When an iron film of 3-5 nm represented the catalyst thickness for growing FWCNT arrays, SWCNTs were synthesized by decreasing the catalyst thickness to 1 nm. The nanotubes were characterized by field emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Electron field emission properties of the nanotubes indicate that the SWCNTs exhibit lower turn-on field compared to the FWCNTs, implying better field emission performance.     

Demonstration of a transient-gain nickel-like xenon-ion x-ray laser

We demonstrate a high-gain nickel-like xenon-ion x-ray laser, using a picosecond-laser-irradiated gas-puff target. The elongated x-ray laser plasma column was produced by irradiation of the gas-puff target with line-focused double picosecond laser pulses with a total energy of 18 J in a traveling-wave excitation scheme. Strong lasing at 9.98 nm was observed, and a high gain coefficient of 17.4 cm(-1) was measured on the transient collisionally excited 4d-4p , J=0-1 transition for nickel-like xenon ions with target lengths as great as 0.45 cm. A weak nickel-like lasing line at a shorter wavelength of 9.64 nm was also observed, with a gain coefficient of 5.9 cm(-1) .     

多波长线性回归分光光度法同时测定油中的铁、钴、镍

本文提出一种同时测定铁,钴,镍的新方法,即多波长线性回归分光光度法,利用铁与５－Ｂｒ－ＰＡＤＡＰ形成的络合物在７５０ｎｍ处吸收峰不受钴,镍干扰的特点,在７５０ｎｍ处于工作曲线法测定铁的含量,对于钴,镍在５５０－６００ｎｍ内采用多波长线性回归法测定。应用于合成样及油样中铁,钴,镍含量的测定,结果令人满意,回收率为９５．７％￣１０４．３％,相对标准偏差为１．４％￣３．８％。     

1064 nm Nd:YAG激光诱导铁等离子体特征参数的研究

利用1064 nm Nd:YAG激光器研究了激光诱导铁条等离子体的特征参数。为了减小测量误差和谱线自发辐射跃迁几率不确定性带来的计算误差,采用改进的迭代Boltzmann方法精确求解铁等离子体的电子温度为8058 K。Lorentz函数拟合Fe I 376.553 nm得到等离子体的电子数密度为8.71017 cm-3。分析表明等离子体的加热机制主要是逆轫致过程,其吸收系数是0.14 cm-1。实验数据证实激光诱导铁等离子体处于局部热力学平衡状态和光学薄状态。     

Micro patterning of fused silica by laser ablation mediated by solid coating absorption

Precise patterning by laser ablation requires sufficient absorption. For weak absorbers like fused silica indirect methods using external absorbers have been developed. A novel approach using a solid SiO absorber coating is described. Irradiation by an ArF excimer laser (wavelength 193 nm) is leading to ablation of the coating and, at sufficiently high fluence, of the fused silica substrate. The remaining coating in the unexposed areas is removed afterwards by large area irradiation. The fluence threshold for substrate ablation using a 28 nm thick absorber layer is about 1.1 J/cm². Single pulse ablation rates of up to 800 nm and a surface roughness of R _a<5 nm are obtained. High resolution grating patterns with 400 nm period and a modulation depth of 80 nm are possible. The process can be described as controlled plasma mediated ablation.     

Er离子注入GaP,GaAs, InP的二次离子质谱(SIMS)的研究

近年来掺稀土元素的Ⅲ—Ⅴ族化合物研究在基础物理和器件应用方面都越来越引起人们的关注,[1,2]其中又由于Er3+的4I13/2—4I15/2的特征发光波长为1.54μm,恰好对应于石英光纤的低损耗区,且离子注入技术简单易行,因而倍受重视.国际上已报道了不少有关Er注入Ⅲ—Ⅴ族化合物的研究,大多选用较低的注入剂量(约1012～1014Er/cm2),而对较高剂量的注入有待于进一步研究.     

Iodine hyperfine structure and absolute frequency measurements at 565, 576, and 585 nm

The hyperfine structure splittings of the P(10)14-1, R(15)14-1, and R(99)15-1 transitions at 585 nm, P(62)17-1 at 576 nm, and P(80)21-1 at 565 nm in ¹²⁷I₂ are measured by heterodyne spectroscopy using two dye lasers. In addition, the absolute frequencies of the hyperfine components P(10)14-1 a₁₅ and P(80)21-1 a₁₀ are determined using a self-referenced frequency comb. These frequencies are used in an experiment testing relativistic time dilation by laser spectroscopy on a fast ion beam.     

Iron oxide nanoparticle synthesis in aqueous and membrane systems for oxidative degradation of trichloroethylene from water

The potential for using hydroxyl radical (OH^?) reactions catalyzed by iron oxide nanoparticles (NPs) to remediate toxic organic compounds was investigated. Iron oxide NPs were synthesized by controlled oxidation of iron NPs prior to their use for contaminant oxidation (by H₂O₂ addition) at near-neutral pH values. Cross-linked polyacrylic acid (PAA) functionalized polyvinylidene fluoride (PVDF) microfiltration membranes were prepared by in situ polymerization of acrylic acid inside the membrane pores. Iron and iron oxide NPs (80–100 nm) were directly synthesized in the polymer matrix of PAA/PVDF membranes, which prevented the agglomeration of particles and controlled the particle size. The conversion of iron to iron oxide in aqueous solution with air oxidation was studied based on X-ray diffraction, Mössbauer spectroscopy and BET surface area test methods. Trichloroethylene (TCE) was selected as the model contaminant because of its environmental importance. Degradations of TCE and H₂O₂ by NP surface generated OH^? were investigated. Depending on the ratio of iron and H₂O₂, TCE conversions as high as 100 % (with about 91 % dechlorination) were obtained. TCE dechlorination was also achieved in real groundwater samples with the reactive membranes.     

Dramatic enhancement of optical-field-ionization collisional-excitation x-ray lasing by an optically preformed plasma waveguide

Dramatic enhancement of optical-field-ionization collisional-excitation x-ray lasing is achieved by using an optically preformed plasma waveguide. With a 9-mm-long pure krypton plasma waveguide prepared by using the axicon-ignitor-heater scheme, lasing at 32.8 nm is enhanced by 400 folds relative to the case without the plasma waveguide. An output level of 8 x 10(10) photon/shot is reached at an energy conversion efficiency of 2 x 10(-6). The same method is used to achieve x-ray lasing in a gas jet for the high-threshold low-gain transition at 46.9 nm in neonlike argon.