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81.
The generation of ultrasound in film–substrate system by a laser line source is studied in the case of ablation mechanism, which can be realized by adding a liquid layer at the excitation point. The time domain displacement can be yielded by the numerical jointed inversed Laplace–Fourier transformation technique. The typical surface acoustic waves (SAW) of two layer structures, slow film on fast substrate and fast film on slow substrate, are obtained and the effect of the propagation distance and the thickness of the film on the SAW are given. 相似文献
82.
U.D. Rapol A. Krishna V. Natarajan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):185-188
We demonstrate a technique to measure hyperfine structure using a frequency-stabilized diode laser and an acousto-optic modulator
locked to the frequency difference between two hyperfine peaks. We use this technique to measure hyperfine intervals in the
5
P
3/2
state of 85Rb and obtain a precision of 20 kHz. We extract values for the magnetic-dipole coupling constant A
= 25.038(5) MHz and the electric-quadrupole coupling constant B
= 26.011(22) MHz. These values are a significant improvement over previous results.
Received 6 March 2003 Published online 15 April 2003 相似文献
83.
Sharmistha Dutta Choudhury 《Journal of luminescence》2007,124(1):33-38
Laser flash photolysis of phenazine (PZ) solution reveals the existence of a stable species with a long lifetime at 380 nm in addition to the usual triplet PZ at 440 nm. The former is suggested to be due to formation of triplet PZ excimer. The triplet excimer also undergoes photoinduced electron transfer with some aromatic amines. The formation of PZ dimer anion radical and amine cation radicals are confirmed by external magnetic field effect studies. Measurement of B1/2, which estimates hyperfine present in the system, also supports this assignment. 相似文献
84.
闪光灯泵浦的Nd:KGd(WO4)2激光器 总被引:1,自引:0,他引:1
报道了用闪光灯泵浦的掺钕的钨酸钆镓(Nd3+:KGd(WO4)2激光器.在重复频率1Hz,脉宽120μs的灯泵下,测量了不同透过率下激光输出能量,获得最大输出能量384mJ,斜率效率1.0%,外推阈值0.54J.在调Q运行时,Nd:KGW晶体的斜率效率为0.16%,最大输出能量46mJ. 相似文献
85.
86.
激光激发的声表面波为材料表面缺陷的检测提供了有力的工具.针对含缺陷材料在模型边界上的复杂性,建立了基于平面应变的有限元模型并选取了相同厚度但含有不同深度的表面裂痕的单层铝板进行了对比计算,得到了声表面波经过不同深度的表面裂痕时产生的反射及透射信号波形的时域特征.进而引入了基于Wigner-Ville分布理论的时-频分析方法计算裂痕前、后散射的瞬态表面波的能量在时间-频率平面内分布的情形.结果显示:声表面波接近中心频率的某一频率成分在经过深度小于其中心波长的表面缺陷时,随着裂痕深度的增加,对应于该频率的反射系数呈现单调递增的趋势;而透射系数呈现递减的特征,这一结果可以为激光超声检测表面缺陷提供一种定量的表征手段. 相似文献
87.
在当前激光核聚变实验中,中子集中在短时间内出现、且产额低。为适应这种特点,要求探测器的效率高,分辨时间短。利用闪烁中子探测器探测激光核聚变所产生的中子,能测定中子产额,记录中子能量,而且探测效率高,分辨时间短。缺点是易受γ射线、X射线的干扰。 相似文献
88.
Rebuilding of metal components with laser cladding forming 总被引:4,自引:0,他引:4
Laser cladding forming (LCF) is a novel powerful tool for the repairing of metal components. Rebuilding of V-grooves on medium carbon steel substrates has been carried out with laser cladding forming technique using stainless steel powder as the cladding material. Microstructure of the deposited layers has been characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDAX), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Mechanical properties of the rebuilt V-groove samples have been evaluated by tensile and impacting tests and microhardness measurement. Experimental results show that good fusion bonding between the rebuilt layers and the substrate has been formed, and the microstructure of the cladding layers is mainly composed of fine, dense and defect-free epitaxial columnar dendrites. Due to the effect of grain size refinement, the tensile strength, impacting toughness, elongation and microhardness of the rebuilt samples have been greatly enhanced compared to those of the substrate. Microhardness is also very uniform throughout the rebuilt regions. With the growth of the deposited layers, the microhardness increases gradually. The good ductility of the deposited regions is verified by the SEM fracture analysis. 相似文献
89.
R. Cristescu G. Dorcioman E. Axente A. Moldovan T. Kocourek M. Albulescu D. Mihaiescu D.B. Chrisey 《Applied Surface Science》2006,252(13):4647-4651
We report the first successful deposition of triacetate-pullulan polysaccharide thin films by matrix assisted pulsed laser evaporation. We used a KrF* excimer laser source (λ = 248 nm, τ ≈ 20 ns) operated at a repetition rate of 10 Hz. We demonstrated by FTIR that our thin films are composed of triacetate-pullulan maintaining its chemical structure and functionality. The dependence on incident laser fluence of the induced surface morphology is analysed. 相似文献
90.
激光对生物分子的共振激发作用 总被引:7,自引:0,他引:7
在生物分子的“谐”和“非谐”振子势模型的基础上,用量子力学讨论了激光对生物分子的共振激作用;并用之对激光的生物激活、诱变机理的“共振吸收”定性理论作一解析分析。 相似文献