Calibration-Free Laser Spectral Analysis of Glasses and Copper Alloys

The calibration-free variant of the laser spectral analysis of the material of solid metal and dielectric samples has been evaluated with the example of determining the component composition of certified copper alloys, an optical filter, a crystal sample with known compositions, and fragments of glass jewelry of archeological origin. It has been shown that there is a good agreement between the measurement and reference data for macrocomponent concentrations (10% and more). Discrepancies have been found between the concentrations of components with a small content (1–5%) in the analyzed sample. All the stages and characteristic features of the methods of calibration-free analysis have been analyzed with specific examples.     

Dynamics of the Emission of Light by C2 and C3 Molecules in a Laser Plasma Produced by Two-Pulse Irradiation of the Target

The laser plasma produced by irradiation of a graphite target simultaneously by the first and second harmonics of two Nd³⁺:YAG lasers has been studied by emission spectroscopy methods. The delay between radiation pulses () varied from 0 to 700 sec. It is established that in the absence of a delay between pulses ( = 0) the increase in the intensity of plasma emission at the wavelengths corresponding to the radiative transitions of the C₂ and C₃ molecules is of nonradiative character. The plasma produced by laser radiation at the wavelength = 1064 nm exerts its influence on the radiation spectrum of the plasma produced by laser radiation at the wavelength = 532 nm, if the magnitude of the delay between laser pulses does not exceed 30 sec. The most probable reason for this character of influence of the prepulse on the laser plasma radiation spectrum is sublimation of soot particles caused by laser radiation at = 532 nm.     

激光烧蚀金属表面产生的发射光谱分析

用观测时间和空间分辨发射光谱的方法研究了脉冲激光烧蚀金属铝靶过程中产生的等离子体羽的特性，计算了其膨胀速度，讨论了大气中等离子体点燃的机制。     

Studies of Metals in Crocodilians by Spectrochemical Methods

Abstract: This review covers the results of metal determinations using various spectrochemical analytical techniques in crocodilians from various geographical regions. The most widely determined metal is mercury, both inorganic and organic. However, many other metals, including the known toxic metals of lead and cadmium, have been determined. In general, more elevated levels of metals have been determined in crocodilians from potentially contaminated as opposed to more pristine areas. Significant differences in concentrations for many metals have been demonstrated in captive versus wild alligators. The part of crocodilians most widely utilized for food, tail or tail meat, has attracted the most interest, but studies on kidney and liver as well as blood have been reported. Eggs and hatchings have also been examined for several metal concentrations.     

飞秒强激光与欠稠密等离子体相互作用中的二次谐波辐射

对超短超强激光脉冲 (45fs,6× 10 17W /cm2 )与光致电离氦气形成的欠稠密等离子体相互作用中的二次谐波辐射进行了实验研究。测量了多种打靶强度的飞秒激光脉冲与不同气体密度氦气相互作用的二次谐波光谱 ,得到在欠稠密等离子体中二次谐波辐射与打靶激光能量的关系 ,分析了产生二次谐波辐射产生的物理机制 ,在考虑了强短脉冲激光电离气体产生的等离子体径向电子密度梯度因素 ,基于非线性作用过程的理论预期曲线与实验结果较好地吻合     

A New Synthetical Model of High-Power Pulsed Laser Ablation

We develop a new synthetical model of high-power pulsed laser ablation, which considers the dynamic absorptance, vaporization, and plasma shielding. And the corresponding heat conduction equations with the initial and boundary conditions are given. The numerical solutions are obtained under the reasonable technical parameter conditions by taking YBa2CusO7 target for example. The space-dependence and time-dependence of temperature in target at a certain laser fluence are presented, then, the transmitted intensity through plasma plume, space-dependence of temperature and ablation rate for different laser fluences are significantly analyzed. As a result, the satisfactorily good agreement between our numerical results and experimental results indicates that the influences of the dynamic absorptance, vaporization, and plasma shielding cannot be neglected. Taking all the three mechanisms above simultaneously into account for the first time, we cause the present model to be more practical.     

A New Synthetical Model of High-Power Pulsed Laser Ablation

We develop a new synthetical model of high-power pulsed laser ablation, which considers the dynamic absorptance, vaporization, and plasma shielding. And the corresponding heat conduction equations with the initial and boundary conditions are given. The numerical solutions are obtained under the reasonable technical parameter conditions by taking YBa₂Cu₃O₇ target for example. The space-dependence and time-dependence of temperature in target at a certain laser fluence are presented, then, the transmitted intensity through plasma plume, space-dependence of temperature and ablation rate for different laser fluences are significantly analyzed. As a result, the satisfactorily good agreement between our numerical results and experimental results indicates that the influences of the dynamic absorptance, vaporization, and plasma shielding cannot be neglected. Taking all the three mechanisms above simultaneously into account for the first time, we cause the present model to be more practical.     

Spectral Standard-Free Laser Microanalysis of Gold Alloys

A standard-free variant of spectral laser microanalysis of the material of gold alloys for determining the standard of fineness of the specimens investigated has been implemented experimentally. A good correspondence of the results of measurements of the concentrations of gold in the materials analyzed to the specified data is shown. The basic stages and characteristic features of the procedures of the standard-free analysis are considered. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 352–357, May–June, 2005.     

飞秒激光烧蚀硅表面产生等离子体的发射光谱研究

对中心波长为800 nm,脉宽为100 fs的激光脉冲烧蚀空气中硅(111)产生的等离子体发射光谱进行了时间和空间分辨研究. 结果表明,在等离子体羽膨胀初期(小于50 ns时间范围内),等离子体发射光谱主要由连续光谱构成,此后连续光谱强度逐渐减弱,线状光谱开始占主导地位;在羽体膨胀过程中离子谱线的存在时间短于原子谱线的存在时间. 由时间分辨发射光谱发现在羽体膨胀过程中等离子体辐射波长存在红移现象,波长红移量随时间演化呈二次指数衰减. 最后给出等离子体发射光谱谱线强度的时空演化规律. 关键词： 飞秒激光 脉冲激光烧蚀 等离子体 发射光谱     

低真空下紫外激光烧蚀铜诱导发光的机理

采用时间与空间分辨的光谱测量技术,测量了在低真空下XeCl紫外激光烧蚀金属Cu诱导产生等离子体发光羽的发射光谱随时间和空间的强度分布,利用快速同步照相的方法获得了发光羽的相片,结果发现发光羽的不同区域有不同的颜色特征。根据实验结果建立了非常可能的激光烧蚀诱导发光的理论模型,认为不同区域的主要发光机理不同,连续辐射背景光来自近靶处高能电子的运动而产生的轫致辐射;原子线的产生来自电子碰撞传能以及电子与离子的复合激发;离子线的产生来自电子与离子碰撞传能激发。此模型不仅能解释单一激发模型所能解释的实验现象,而且还能够很好地解释单一模型所不能解释的实验现象,低真空下紫外激光烧蚀铜诱导发光的机理与常压下相似,在此实验条件下可以更准确地揭示诱导发光的机理。     

发射光谱法研究纳秒激光烧蚀硅等离子体特性

利用调Q Nd3+∶YAG激光器三倍频355 nm激光脉冲烧蚀空气环境的硅样品,观测不同脉冲激光能量下产生的等离子体在380～420 nm范围内的时间-空间分辨等离子体发射光谱,观测到在等离子体羽膨胀初期存在N+发射光谱。在局域热力学平衡近似条件下,根据时间-空间分辨等离子体发射光谱计算得到等离子羽体电子温度和电子密度随时间延时存在二次指数衰减变化,等离子体羽体电子温度和电子密度的空间分布近似呈Lorentz分布,发现在确定激光脉冲能量下电子密度空间分布最大值偏离光谱强度最大空间位置并对产生原因进行分析,探讨了等离子体羽参数与激光脉冲能量的关系。     

基于脉冲CO2激光锡等离子体光刻光源的极紫外辐射光谱特性研究

研究了不同条件下脉冲放电CO₂激光烧蚀平板锡靶产生的等离子体极紫外辐射特性, 设计并建立了一套掠入射极紫外平焦场光栅光谱仪, 结合X射线CCD探测了光源在6.5～16.8 nm波段的时间积分辐射光谱,得到了极紫外光谱随激光脉宽, 入射脉冲能量及背景气压的变化规律。实验结果发现：入射激光脉冲能量在30～600 mJ变化时,极紫外辐射光谱的强度随辐照激光脉冲能量的增加而增加, 但并不是线性关系, 具有饱和效应, 且产生极紫外辐射的脉冲能量阈值约为30 mJ,当激光脉冲能量为425 mJ时具有最高的转换效率,此时中心波长13.5 nm处2%带宽内的转换效率约为1.2%。激光脉冲半高全宽在50～120 ns范围内变化时, 极紫外辐射光谱的峰值位置均位于13.5 nm,光谱形状几乎没有什么变化, 但是脉宽从120 ns变到52 ns后,由于激光功率密度的提高,极紫外辐射强度也随之增强了约1.6倍。极紫外光谱的强度随背景气压的增大而迅速下降, 当腔内空气气压为200 Pa时, 极紫外辐射光子几乎被全部吸收,而当缓冲氦气气压为7×104 Pa时,仍能够探测到微弱的极紫外辐射信号,计算表明100 Pa的空气对13.5 nm极紫外光的吸收系数为3.0 m-1,而100 Pa的He气的吸收系数为0.96 m-1。     

Wavelength Shift Investigation of Optical Emission from Nanosecond Pulsed Laser Ablated Metal Al

The wavelength shift of optical emission from pulsed laser ablation of metal Al in 1atm air has been investigated by using the time-resolved optical emission spectroscopy (OES). The wavelength shift of OES has a second order exponential decay with time and was also found to be significantly influenced by the laser ablated pulse energy. By taking account of the shielding effect of free electrons inside of the plasma plume, the relation between the electron density and wavelength shift has been discussed.     

脉冲激光烧蚀Ge产生等离子体特性的数值模拟

针对激光烧蚀半导体材料Ge初期的特点,建立了1维的热传导和流体动力学模型。对波长为248 nm、脉宽为17 ns、峰值功率密度为4×108 W/cm2的KrF脉冲激光在133.32 Pa氦气环境下烧蚀Ge产生等离子体的特性进行了数值模拟。结果表明：单个激光脉冲对靶的烧蚀深度达到55 nm,蒸气膨胀前端由于压缩背景气体产生压缩冲击波, 波前的速度最大,温度很高。从不同时刻的电离率分布图中得出,在靶面附近区域,Ge的1阶电离始终占优势;在中心区域,脉冲作用时间内,Ge的2阶电离率比1阶电离率大,脉冲结束后,Ge的2阶电离率下降,1阶电离率逐渐变大。     

Spectrochemical Determination of Microimpurities in Mercury

Abstract

Mercury together with the microimpurities in it had been turned into iodides in advance in a vacuum ampule in the presence of collector - spectrally pure carbon powder, containing 2 per cent Li (as Li₂CO₃). The obtained mercury (II) iodide was separated from the microimpurities by sublimation at 100°C and the collector with the microimpurities was subjected to spectral analysis. The method allows the determination of 20 elements in mercury within detection limits of 10^?5 to 10^?7% and relative standard deviation 0.08 to 0.25. The method can be applied for the analysis of mercury (II) iodide, too.     

脉冲激光制备类金刚石薄膜及原位激光等离子体发射光谱

用ＹＡＧ脉冲激光轰击真空室内的石墨靶,可以形成包含碳素的激光等离子体,并在硅或石英衬氏上淀积形成某种类型的碳膜。用光学多道分析仪原位测量了激光等离子体的发射光谱,给出反应空间可能存在的反应基团有碳原子、碳离子、碳分子等,用拉曼光谱研究了薄膜的结构,证明所形成的薄膜为类金刚石膜,并得出碳原子和碳离子与薄膜的类金刚石结构有关。制备过程中,氢的参与有利于薄膜中金刚石成分的形成。空间分辨的原位激光等离子体发射光谱表明,在反应空间存在薄膜形成的最佳位置。     

Laser plasma plume kinetic spectroscopy of the nitrogen and carbon species

The formation and decay of carbon and nitrogen atoms, CN radicals and C₂ molecules were monitored using spatial‐ and time‐resolved emission spectroscopy in a plasma plume formed during laser ablation of a graphite target in nitrogen atmosphere. A simple exponential model was used to explain the effect of the individual chemical reactions and plasma dynamics on the measured kinetic characteristics. The succession of emissions C → N → CN was observed in the time‐resolved spectra, supporting the suggestion that the CN radical is formed mainly by the direct reaction C + N → CN or C₂ + N₂ → 2CN. The formation of CN radical was enhanced by the additional generation of atomic nitrogen through the RF discharge. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of Nano-Cadmium Sulfide by Pulsed Laser Ablation in Liquid Environment

A pulsed laser-assisted in liquid environment method has been developed successfully to synthesize size-tunable (5–12 nm) and different shapes (sphere, rod, rope) of nano II–VI semiconductor (cadmium sulfide). This method can be carried out in two ways; the first one is the top-down technique, which has been discussed in publications in the last few decades, and the other one is the bottom-up technique, which appears for the first time in this paper. X-ray diffraction, ultraviolet-visible spectroscopy, and transmission electron microscopy confirm that the nanoparticles are crystalline. The methods lead to the production of nanomaterials, which are important for photonics and biosensing applications. Both synthesized methods can be applied in all materials because of their ability to ablate almost all kinds of materials due to the ultrahigh energy density and control over the growth process by manipulating the process parameters such as intensity, wavelength, and so on.     

准分子激光取样与电感耦合等离子体质谱和光谱联用分析仪器研究进展

将准分子激光剥蚀取样后的产物经由电感耦合等离子质谱与光谱分析,从而获得被激光剥蚀样品的元素与同位素含量信息,是迄今为止适应于表面原位微区分析最为重要的分析科学技术手段之一.基于准分子激光剥蚀取样技术分别与电感耦合等离子体质谱或发射光谱技术联用的分析手段,已经被广泛应用于地质学、材料学、环境科学,甚至生命科学领域的原位微...     

脉冲激光沉积方法制备ZnO薄膜生长参量对发光特性的影响

用脉冲激光沉积（PLD）方法在Si（111）衬底上制备了ZnO薄膜。以325nmHe-Cd激光器为光源对薄膜进行了荧光光谱分析,用X射线衍射仪（XRD）和原子力显微镜（AFM）分别对薄膜的结构和形貌进行了分析。脉冲激光沉积方法的主要生长参量为氧压、激光重复频率、生长温度和激光能量。通过控制这些参量变量,研究了这些参量对ZnO薄膜发光特性的影响,得到了用于紫外发光的ZnO薄膜生长的优化条件：发现在温度为650℃左右、氧压50Pa左右、频率5Hz左右的范围内能得到半峰全宽较窄,强度较大的紫外发光峰。分析认为紫外峰主要是由激子辐射复合发光形成的,绿光带主要和Ozn的存在密切相关,氧空位是蓝光发射的重要原因。