共查询到18条相似文献,搜索用时 484 毫秒
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具有液氮温度和适度压强的氢气通过S99阀门Laval喷嘴进入真空,经超声绝热膨胀形成团簇。本实验用瑞利散射法测量氢团簇尺寸随阀门背压强的变化曲线。当背压为1.0MPa时,每个氢团簇平均包含250个氢原子。 相似文献
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利用飞行时间谱,研究了在飞秒强激光场(60 fs,2×1016 W/cm2)作用下,大尺寸氩原子团簇Arn(n—=3×103—3×106原子/每团簇)的电离爆炸过程,测量了 团簇爆炸所产生的氩离子的平均能量与团簇尺寸(气体背压)的关系.实验发现,随着气体 背压的升高(团簇尺寸增大),氩离子的平均能量也相应升高.通过分析两个不同几何尺寸 锥形超声喷嘴所产生团簇爆炸后的离子能量,结合Hagena团簇尺寸规律,发现在激光参数保 持不变的情况下,离子的平均能量由团簇尺寸唯一确定.分析表明,团簇尺寸在3×105原 子/每团簇以下时,团簇膨胀的主要机理是库仑爆炸.随着团簇尺寸的进一步增大,团簇膨胀 机理将由库仑爆炸向流体动力学膨胀过渡,在3×105关键词:
原子团簇
飞秒强激光
库仑爆炸
流体动力学膨胀 相似文献
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团簇源特性是影响激光与团簇相互作用的一个主要因素,因此团簇源的特性研究是一项非常关键的工作.本文主要从以下两个方面对气体团簇形成过程进行模拟计算:①从流体力学角度出发,讨论气体的密度、压强及温度在喷嘴轴线上的空间分布,结合汽液平衡方程分析团簇开始形成的位置;②采用液滴模型,讨论团簇尺寸随时间的变化.这些结果不仅有利于进一步研究团簇形成过程的特性,而且为激光与团簇相互作用实验的设计提供宝贵的参考. 相似文献
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蔡晓红 邵曹杰 卢荣春 李明生 阮芳芳 詹文龙 Yu.V.Shestakov D.K.Torpokov R.S.Sadykov S.A.Zevakov 《中国物理 C》2007,31(8):750-754
为HIRFL-CSR团簇内靶设计加工了新的供气系统, 拆换了原有的喷嘴, 对氢气和氩气进行了新的实验, 获得了氢气和氩气的稳定团簇束, 解决了困扰团簇靶稳定运行的喷嘴堵塞问题. 获得的氢团簇束密度为1.75×1013 atoms/cm3, 好于德国GSI内靶对氢束所达到的1×1013atoms/cm3. 研究了团簇束的衰减, 测量了氢束和氩束的有效靶厚, 研究了团簇靶系统对这两种工作气体的长期运行稳定性. 对氢和氩两种工作气体, 各级气压呈现了良好的稳定性, 说明在实验的时间范围内, 团簇靶运行稳定. 相似文献
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本文通过对高背压(50 bar, 1 bar = 1.0×105 Pa)氩气经长锥型喷嘴(长度L=30 mm)向真空绝热膨胀所形成的超声气体团簇喷流的数值模拟, 分析比较了由喷嘴喉口起沿喷流方向在喷流中心轴线上团簇平均尺寸的演化情况. 结果表明: 沿喷流方向团簇平均尺寸显示先增长后趋于饱和的变化趋势, 具有较大尺寸团簇的区域出现在距离喷嘴喉口大约20 mm. 据此本文再结合关于喷流中原子密度沿喷流方向变化的模拟结果开展了锥形喷嘴长度的优化研究. 针对由常见构型的锥形喷嘴(喉径~ 0.5 mm, 半张角~ 8.5°)在高背压下形成的团簇喷流, 20 mm左右的长度为锥形喷嘴的适宜长度. 相似文献
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大气压氩直流微放电光谱研究 总被引:1,自引:1,他引:0
微空心阴极放电或微放电是一种能够实现高气压下放电的有效方法。利用不锈钢空心针作阴极,不锈钢网作阳极,进行了大气压氩直流微放电实验研究。测量了大气压氩微放电光谱,发现氩气的发 射谱线主要集中在690~860 nm范围,且全部为氩原子4p—4s的跃迁。实验研究了不同放电电流、气体压强、气体流量与谱线强度之间的关系,发现谱线强度随放电电流、气体流量增加均增加,而谱线强 度随压强变化呈现不同特征:谱线强度随压强的增加先增加后降低,在13.3 kPa时强度最大。此外,选用跃迁波长为763.51和772.42 nm的两条光谱线,利用发射谱线强度比值法测量了氩气微放电等离子 体的电子激发温度。结果显示,其电子激发温度处于2 000~2 800 K之间,且随放电电流的增加而增加,随气体压强和气体流量的增加而降低。 相似文献
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Noble gases (argon, krypton, and xenon) are puffed into vacuum through a nozzle to produce clusters for studying laser-cluster interactions. Good estimates of the average size of the argon, krypton and xenon clusters are made by carrying out a series of Rayleigh scattering experiments. In the experiments, we have found that the scattered signal intensity varied greatly with the opening area of the pulsed valve. A new method is put forward to choose the appropriate scattered signal and measure the size of Kr cluster. 相似文献
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J. F. Han C. W. Yang J. W. Miao J. F. Lu M. Liu X. B. Luo M. G. Shi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(3):347-352
The spatial distribution of argon clusters in gas jet is tested using the Rayleigh scattering method. A pulsed laser is used
to acquire the whole evolution of the cluster inside one event. The measured results at a fixed axial position show that the
argon clusters grow in less than one millisecond after the nozzle is opened and the cluster size keeps constant during the
whole open period of 20 ms. Further results show that the scattering signal along the radial direction is almost Gaussian-distributed
and the full width half maximum (FWHM) increases almost linearly when the distance from nozzle increases. The scattering signal
along the axial direction is Landau-distributed and the area near the nozzle is most effective for laser cluster interaction. 相似文献
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J. W. Hewage F. G. Amar M.-F. de Feraudy G. Torchet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):249-252
Using realistic pair potentials, we investigate the
structures of mixed clusters of argon and nitrogen in order to
interpret the experimental electron diffraction patterns
reported by the Torchet group. Simulations of small clusters
indicate that argon tends to segregate at the center of the
clusters. For larger clusters, in the range of 50 to 200
molecules, MC methods have been used to simulate structures that
are likely to be generated in the molecular beam. By comparing
predicted electron diffraction patterns with those recorded in
the experiments, our models allow us to estimate the average
size and composition of the mixed clusters for a given set of
experimental conditions (nozzle stagnation pressure and Ar
partial pressure). 相似文献
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YAO Lianghua FENG Beibing CHEN Chengyuan NI Guoquan LU Halyang RAN Hong 《核工业西南物理研究院年报(英文版)》2006,(1):41-42
The hydrogen clusters are produced at liquid nitrogen temperature in a supersonic adiabatic expansion of moderate backing pressure gases into vacuum through a Laval nozzle and their averaged size are measured by Rayleigh scattering. The average cluster size N^-c is about 250 hydrogen atoms at a backing pressure 1.0 MPa in these measurements. 相似文献
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The experimental parameters that control the surface morphology and size of iron cobalt nanoparticles synthesized at room temperature by pulsed laser ablation deposition (PLAD) technique have been systematically investigated. The nanoparticle synthesis has been achieved at higher operating gas pressures of argon. It was found that nanoparticles upon deposition formed small clusters, the size of which increases with decreasing pressure, increasing laser-energy density, and decreasing target-to-substrate distance. This trend could be attributed to change in the kinetic energy of deposited nanoparticles with varying argon pressure, laser-energy, and target-to-substrate distance. The nanoparticles size and size distribution showed strong dependence on argon pressure and weak dependence on laser-energy density and target-to-substrate distance. 相似文献
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Ni Guoquan Li Zhong Lei Anle Xu Zhizhan 《Chinese Journal of Lasers》2001,10(2):117-122
Duringthepastyearsarevolutionhasemergedtoproduceultrashortandextremelyhigh intensitylaser pulseswiththedevelopmentofthetechniqueofchirpedpulseamplification (CPA ) [1] .Concurrently ,theavailabilityoftheultrashortintense pulsesopensanewregimeofstrongfield mat… 相似文献
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With a 45 fs multiterawatt 790 nm laser system and jets of argon and krypton atomic clusters, a study of the interaction of fs intense laser pulses with large size rare gas dusters was conducted. The maximum laser intensity of about 7 × 1016 W/cm2 and dusters composed of thousands of atoms which were determined through Rayleigh scattering measurements were involved inthe experiments. On the one hand, the results indicate that the interaction is strongly cluster size dependent. The stronger the interaction, the larger the clusters are. On the other hand, a saturation followed by a drop of the energy of ions ejected from the interaction will occur when the laser intensity exceeds a definite value for clusters of a certain size. 相似文献
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The internal energies and compressibility factors of argon, krypton and xenon have been simulated using recent state-of-the-art ab initio pair intermolecular potentials and the best semi-empirical pair potentials, and the Axilrod-Teller-Muto three-body term. The results are compared with experimental data for both sub-critical and super-critical temperatures and for densities ranging up to a 2.5 multiple of the critical density. Both the ab initio and semi-empirical results for argon are in very good agreement with the experimental ones. For krypton and xenon, the ab initio results are worse than the semi-empirical results but they are still acceptable. 相似文献