激光诱导氩气等离子体时间分辨特性研究

激光诱导击穿光谱(L IB S)以激光诱导微等离子体的原子发射为技术特征,在科研与工业领域正得到重视与蓬勃发展.作为环境气体的氩气对等离子体演化过程中粒子的碰撞过程有重要影响,决定着L IBS技术分析性能的发挥.利用光谱诊断技术深入研究LIBS技术条件下氩气的光谱特征,对于提升LIBS技术及其应用水平具有重要的意义.利...     

远程激光诱导击穿光谱技术与应用(特邀)

在冶金工业、核工业、深空探测等领域,受限于高温、强辐射等人员无法达到的极端环境限制,亟需一种可快速准确进行物质成份分析的远距离非接触式探测手段。远程激光诱导击穿光谱技术是一种结合激光远距离传输与控制以及弱光信号采集来获取目标材料物质成份信息的一种技术手段,可以实现极端环境下物质的非接触式远距离探测。本文系统介绍了远程激光诱导击穿光谱系统的光学系统结构,以及不同结构远程激光诱导击穿光谱装置的性能特点及其面临的技术瓶颈。针对远程激光诱导击穿光谱技术探测灵敏度与探测距离受限、光谱信息受限等问题,还介绍了国内外常用的远程激光诱导击穿光谱信号增强方法以及激光诱导击穿光谱与拉曼光谱结合等技术方法。最后简要总结了远程激光诱导击穿光谱技术在爆炸物探测、核工业、深空探测等几个典型领域的应用,展望了其在未来的发展。     

基于共振激发的激光诱导击穿光谱技术研究进展

激光诱导击穿光谱技术是一种新型的原子光谱分析技术,具有实时快速、 多元素同时分析和样品预处理简单等特点,从一出现便受到研究人员的广泛关注,但分析灵敏度差一直是限制该技术发展的重要因素。基于共振激发的激光诱导击穿光谱技术将原子荧光光谱技术和激光诱导击穿光谱技术结合,对目标元素进行选择性激发,可以大幅提高激光诱导击穿光谱技术的分析灵敏度,极大地拓展了LIBS技术在痕量元素检测领域的应用。本文综述了基于共振激发的激光诱导击穿光谱技术的研究进展,介绍了激光诱导等离子体中荧光光谱的产生过程以及基于共振激发的激光诱导击穿光谱技术的基本类型和基础原理,详细分析了烧蚀激光能量、 共振激发激光能量和波长、 烧蚀激光和共振激发激光之间的延时以及光谱采集门宽对光谱增强效果的影响,阐述了其在冶金、 环境监测、 同位素检测等领域的应用现状和存在的问题,并对其未来发展前景进行了展望。     

激光光谱技术在环境监测中的应用专题系列(Ⅰ) 光谱技术在大气环境监测中的应用

碳的氧化物、硫的氧化物、氮的氧化物和卤化物等是由人类的生产活动和社会活动产生的重要的环境污染物质 .它造成了温室效应、酸雨、对流层的光化学雾和平流层的臭氧耗减等环境问题 .它威胁着人类的生存环境和地球上的生态平衡 .光谱技术可广泛应用于环境污染监测 .文章简要介绍全球面临的主要环境问题 ,重点介绍光谱技术 (包括常规光谱技术、激光光谱技术以及激光雷达等 )在大气环境监测中的应用和进展 .利用这些技术 ,可以获得污染物的组分、浓度、温度或空间分布等方面的信息 .     

激光诱导击穿光谱技术的研究与应用新进展

激光诱导击穿光谱技术(LIBS)是一种近年来随着激光技术和光谱检测技术的发展而兴起的对元素定性和定量分析的光谱技术。详细介绍了LIBS技术最新的研究发展情况,以及在冶金、环境污染检测、生物医学、植物学、空间探索等领域的最新应用进展。     

激光生物光谱

激光光谱技术有很高的光谱分辨率和分析灵敏度，利用它可以深入地研究生物分子反应动力学及某些生物分子的光化学反应机理，把激光生物学的研究提高到分子水平，有助于阐明生物分子的结构和功能，揭示生命现象的奥秘．本文介绍了激光皮秒光谱、荧光光谱、反射光谱、透射光谱等技术，在研究生物分子、生物细胞、各种生物过程以及诊断癌症等方面的进展及应用前景；同时也介绍了几种生物光谱仪器．     

钛蓝宝石飞秒超快光谱技术及其应用进展

介绍飞秒激光技术的进展、钛宝石飞秒激光放大技术及飞秒分辨相关测量技术.并介绍了飞秒分辨光荧光上转换和光克尔实验技术及其在各种学科中的应用. 关键词： 飞秒激光 飞秒光谱 光克尔 光荧光     

多元线性回归提高激光诱导荧光辅助激光诱导击穿光谱技术的准确度

冶金、核工业、污染检测和环境监测等领域对元素分析的需求是必不可少.激光诱导击穿光谱技术作为一种新型的原子光谱分析技术,具有实时快速、对样品几乎无损、可多元素同时分析等特点,因此一直受到广泛的关注.但其分析灵敏度较差的缺点一直限制着该技术的发展.激光诱导荧光辅助激光诱导激光光谱技术能够通过激光共振激发提高分析灵敏度并高效...     

红细胞内吞银包金纳米颗粒的实时表面增强喇曼研究

研究了结晶紫包裹的银包金纳米粒子进入红细胞的实时过程.利用激光光镊喇曼技术每隔20s通过光镊囚禁红细胞并收集该细胞及邻近溶液的喇曼光谱,抽取光谱中具代表性的特征峰来观察其强度随时间的变化.结果表明:从囚禁的红细胞中收集到的光谱包括了归属红细胞与结晶紫的特征峰.红细胞的光谱特征峰1 001、1 128、1 213cm-1和结晶紫的光谱特征峰915、1 177、1 389、1 586、1 619cm-1的强度随着时间增加,表明在红细胞与纳米粒子共培养的过程中,纳米粒子在红细胞中累积,并引起红细胞信号增强.分析红细胞与其邻近溶液的光谱差,发现归属结晶紫的光谱特征峰913、1 179、1 586cm-1随时间呈类余弦的变化,表明红细胞内的结晶紫包裹的银包金纳米粒子含量先升高后降低再升高.通过计算得到纳米粒子开始进入红细胞的时间范围及进入的速度、被溶酶体降解的速度.研究表明表面增强喇曼技术为研究外物进入细胞提供了新的实验方法和思路.     

燃烧产物组成激光诱导荧光光谱的测量

对激光诱导荧光（LIF）光谱技术在燃烧过程中的应用进行研究，介绍测量燃烧过程中常见自由基OH和NO的LIF光谱的实验方案，以及采用激光诱导荧光光谱技术测量小分子荧光光谱的方法，利用YAG激光器、染料激光器、CO2激光器、光谱仪、ICCD等设备对燃烧产物中常见小分子自由基OH和NO进行了测量，从实验中得到了自由基OH和NO的荧光光谱。实验结果表明，荧光光谱与激发波长无关，但是激发波长改变后，荧光强度因离开最佳波长而有所下降，这符合分子荧光光谱的特征。与其他光谱技术相比，激光诱导荧光光谱技术具有极高的选择性和灵敏度。     

脉冲激光沉积Ag:BaTiO3纳米复合薄膜及其光学特性

在MgO(100)基片上利用脉冲激光沉积技术制备了掺有Ag纳米颗粒的BaTiO₃复合薄膜.通过X射线衍射对薄膜的结构进行了表征,利用透射电子显微镜对Ag纳米颗粒的尺寸、形态进行了观测,X射线光电子能谱结果表明Ag呈金属态.在410—500nm范围内观测到了Ag纳米颗粒引起的等离子振荡峰,随着后处理温度和Ag颗粒浓度的增加,吸收峰发生红移,并出现了双峰现象. 关键词： 金属纳米复合薄膜 激光沉积 光吸收     

亚密度冷等离子体的低功率激光吸收特性分析

当电子密度远低于入射小功率激光所对应的临界密度时,冷等离子体对激光的吸收特性与高密度热等离子体将有很大的差别。在亚密度冷等离子体中,电子与中性粒子间的碰撞将占主导地位,对应的频率远大于电子-离子碰撞频率,这使得碰撞吸收本质发生了变化。亚密度等离子体的电子密度和碰撞频率均较小,它在单位长度传输路径内对常用的工作在可见光、红外波段内的小功率激光的碰撞吸收可以忽略不计。但是对于非正常吸收机制的影响尚需深入研究。     

Absorption and luminescence spectroscopy of fused silica by multiple pulses irradiation at 355 nm

In this work, the effects of laser irradiation on fused silica at 355 nm are investigated by using transient absorption spectroscopy and luminescence spectroscopy. Our result shows that no transient absorption or luminescence in the spectra range from 400 nm to 600 nm is observed when laser energy density is below the damage threshold. When the laser energy density reaches the threshold, an initial damage site will be created. After subsequent laser pulses irradiation, the damage size grows. At the same time, the intensity of the transient absorption and luminescence spectra at the damage site also raises remarkably with the laser pulse number increasing. The absorption band from 420 nm to 520 nm is probably related to the absorption of impurity such as metal ion of iron, cerium and copper. Laser modified fused silica exhibits intense broad luminescence bands due to oxygen-deficiency centers at 444 nm and 580 nm.     

Optimisation of laser linewidth and cavity alignment in off-axis cavity-enhanced absorption spectroscopy

Laser linewidth affects baseline mode structured variations and hence measurement absorption sensitivity in off-axis cavity enhanced absorption spectroscopy with a continuous-wave tunable laser and a stable optical cavity formed by two high reflectivity mirrors. Cavity transmittances have been calculated for various laser linewidths and different optical beam re-entrant conditions for the cavity when overlapping of the optical beams occurs on the cavity mirrors after a finite number of beam round trips within the cavity. It is shown that in order to achieve maximum absorption sensitivity both a specific laser linewidth and specific arrangement of the optical cavity have to be selected and defined using the proposed approach.     

有机材料反饱和吸收特性分析

从能级角度出发,结合入射激光脉宽对粒子吸收方面的影响,用速率方程模拟了各能级粒子数的瞬时变化关系,给出了激光脉宽与能级寿命可比拟时反饱和吸收的动态解,表明粒子在能级上的分布情况。用C60和HITCI(1,1′,3,3,3′,3′hexa methyl lindo tricarbocyanine Iodide)的实验参数理论模拟了激发态吸收截面大于基态吸收截面时透射率随光强的变化关系,用以说明大的上能级吸收截面可以抑制光强过大时引起的饱和吸收,增强材料的非线性光限幅特性。     

Laser intracavity absorption spectroscopy

Emission spectra of multimode lasers are very sensitive to spectrally selective extinction in their cavity. This phenomenon allows the quantitative measurement of absorption. The sensitivity of measurements of intracavity absorption grows with the laser pulse duration. The ultimate sensitivity obtained with a cw laser is set by various perturbations of the light coherence, such as quantum noise, Rayleigh scattering, four-wave mixing by population pulsations, and stimulated Brillouin scattering. It depends on the particular laser type used, and on its operative parameters, for example pump power, cavity loss, cavity length, and length of the gain medium. Nonlinear mode-coupling dominates the dynamics of lasers that feature a thin gain medium, such as dye lasers, whereas Rayleigh scattering is more important in lasers with a long gain medium, such as doped fibre lasers, or the Ti:sapphire laser. The highest sensitivity so far has been obtained with a cw dye laser. It corresponds to 70000 km effective length of the absorption path. The ultimate spectral resolution is determined by the spectral width of mode emission, which is 0.7 Hz in this dye laser. High sensitivity and high temporal and spectral resolution allow various practical applications of laser intracavity spectroscopy, such as measurements and simulations of atmospheric absorption, molecular and atomic spectroscopy, process control, isotope separation, study of free radicals and chemical reactions, combustion diagnostics, spectroscopy of excited states and nonlinear processes, measurements of gain and of spectrally narrow light emission. Intracavity absorption in single-mode lasers shows enhanced sensitivity as well, although not as high as in multimode lasers. Received: 10 May 1999 / Published online: 29 July 1999     

可调谐激光吸收光谱法与气相色谱法监测甲烷的对比研究

甲烷是一种重要的温室气体,它对大气中温室效应的贡献仅次于二氧化碳.针对环境空气中甲烷的测定,从测量原理、测量过程和测量装置等方面比较了可调谐二极管激光吸收光谱和气相色谱法两种测量方法.结果表明用上述两种方法测得的甲烷的日变化趋势具有良好的一致性.相比较而言,后者造价更低,并且更方便.     

环行染料激光器用于内腔吸收光谱的研究

本文报告了利用新型连续波环行染料激光器,即使行波工作于超过阈值两倍以上,仍在大气中获得了近10~5的内腔吸收灵敏放大;并首次利用单频扫描方法,在不降低灵敏放大的同时,得到了10~(-2)的光谱分辨率。实验结果与经改进后的Brunner-Paul理论分析一致。     

Velocity measurements by cavity ringdown spectroscopy

We demonstrate velocity measurements of gas-phase particles by using cavity ringdown spectroscopy (CRDS). Velocity information is inferred from the Doppler-shift contributions to the measured absorption line shape. Because in CRDS the laser beam propagates back and forth within the optical cavity, a measured absorption feature is both upshifted and downshifted; i.e., it is split by the velocity component parallel to the optical axis. The splitting of the absorption features allows direct velocity measurements to be made without requiring an external frequency reference. The CRDS velocity measurement approach is demonstrated for sputtered molybdenum atoms in a low-pressure (collisionless) environment.     

Dynamics of femtosecond-laser-ablated liquid-aluminum nanoparticles probed by means of spatiotemporally resolved X-ray absorption spectroscopy

We investigated spatiotemporal evolution of expanding ablation plume of aluminum created by a 100-fs, 10¹⁴–10¹⁵-W/cm² laser pulse. For diagnosing dynamic behavior of ablation plume, we employed the spatiotemporally resolved X-ray absorption spectroscopy (XAS) system that consists of a femtosecond-laser-plasma soft X-ray source and a Kirkpatrick–Baez (K–B) microscope. We successfully assigned the ejected particles by analyzing structure of absorption spectra near the L _II,III absorption edge of Al, and we clarified the spatial distribution of Al⁺ ions, Al atoms, and liquid droplets of Al in the plume. We found that the ejected particles strongly depend the irradiated laser intensity. The spatial distribution of atomic density and the expansion velocity of each type of particle were estimated from the spatiotemporal evolution of ablation particles. We also investigated a temperature of the aluminum fine particles in liquid phase during the plume expansion by analyzing the slope of the L _II,III absorption edge in case of 10¹⁴-W/cm² laser irradiation where the nanoparticles are most efficiently produced. The result suggests that the ejected particles travel in a vacuum as a liquid phase with a temperature of about 2500 to 4200 K in the early stage of plume expansion.