飞秒强激光脉冲与惰性气体团簇和氢团簇的相互作用研究
文献类型：学位论文
| 作者 | 李邵辉 |
| 学位类别 | 博士 |
| 答辩日期 | 2004 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 徐至展 |
| 关键词 | 飞秒强激光脉冲 团簇 瑞利散射 库仑爆炸 高能离子 |
| 其他题名 | Studies on the Interaction of Femtosecond Intense Laser Pulses with Rare Gas Clusters and Hydrogen Clusters |
| 中文摘要 | 飞秒强激光与物质相互作用研究是当前科学研究的热点前沿之一。随着超短超强激光技术的迅猛发展，在小型化台式激光系统上，目前已经实现了时间宽度只有几飞秒的超短脉冲激光，在可聚焦功率密度方面也可以达到一1护oW/cm2量级。团簇作为一种特殊的物质形态，尺寸介于气体原子、分子到大块固体之间。对团簇与超强超短激光的相互作用开展研究，不仅可以建立从原子、分子到固体更为完整的强场与物质相互作用的微观和宏观物理图像及相应的理论模型，而且有许多潜在的实际应用价值。本论文内容涉及大尺寸惰性气体原子团簇和氢分子团簇喷流的制备和诊断；团簇的电子碰撞电离；以及飞秒强激光脉冲与大尺寸惰性气体团簇和氢团簇喷流的相互作用。研究成果包括以下几个方面：1．大尺寸惰性气体原子团簇和氢分子团簇喷流的制备和诊断利用高背压惰性气体和高背压低温氢气经锥形喷嘴向真空超声绝热膨胀来产生团簇，用Rayleigh散射方法诊断团簇尺寸及团簇喷流的时间特性。得到惰性气体团簇（Arll，Krn，Xen）喷流中的平均团簇尺寸万（每团簇含原子的数目）范围在102-106；氢分子团簇（H2）n的尺寸达到104。首次在Krn和Xen团簇喷流的Rayleigh散射信号时间分辨谱观察到异常的双峰结构，采用三个不同的脉冲气阀一喷嘴装置对该双峰结构及团簇形成的时间演化过程进行了研究。2．大尺寸Krn和Xcn团簇的电子束碰撞电离研究利用离子规管探测器，首次探测到大尺寸Krn和Xen团簇的雪崩电离现象。实验发现，在电子束碰撞电离下，团簇喷流和团簇束流的电子碰撞电离具有强烈的尺寸相关特征。3．惰性气体团簇和氢分子团簇对飞秒强激光脉冲的吸收测量首次进行了大尺寸惰性气体团簇喷流和氢分子团簇喷流对飞秒强激光脉冲的吸收测a实验发现，相对于原子或者分子气体喷流对激光的低吸收效率（小于10％），惰性气体团簇喷流和氢分子团簇喷流对飞秒强激光脉冲有非常强的吸收，吸收效率分别达90％和50％以上。4．Xetl团簇喷流与飞秒强激光脉冲相互作用产生能量达1.3MeV的高能氮离子在最佳团簇尺寸条件下，飞行时间谱探测到飞秒强激光脉冲与xe万、团簇喷流相互作用产生的Xe离子能量高达1.3MeV。Xe离子的平均能量随团簇尺寸变化有一最佳尺寸，超过该尺寸，Xe离子的平均能量反而降低。5．Arn团簇与飞秒强激光脉冲相互作用的爆炸机理研究首次在Arn团簇尺寸跨度达n=3*103-3*100的范围，研究了Arn团簇喷流与飞秒强激光脉冲相互作用引起的团簇“爆炸”机理。实验研究发现，在Arn团簇平均尺寸万＜3x105时，Ar离子平均能量万与万满足E∝n0.5关系，Arn团簇爆炸机制为库仑爆炸。超过这个范围，在n＞3*103时，Ar离子平均能量随团簇尺寸增加而增长的速度趋缓并渐趋饱和，团簇爆炸为团簇离子库仑斥力和流体动力学压力共同作用的结果。6．Arn团簇在飞秒强激光场中爆炸产生的离子能量和产额的空间角分布特征研究A几团簇喷流与飞秒强激光脉冲相互作用实验揭示，Arn团簇爆炸产生的离子能量和产额的空间分布与激光的偏振紧密相关。与激光电场平行方向上Ar离子的平均能量和离子产额比垂直方向上分别高出40％和80％。提出椭球等离子体爆炸模型对此实验结果进行了解释。7．氢分子团簇与飞秒强激光脉冲相互作用的初步研究在高气体背压（尸。达80bar）和低温（近液氮温度）实验条件下制备获得大尺寸（HZ）n（万一104）团簇喷流。（HZ）n团簇喷流与飞秒强激光脉冲的相互作用的初步实验结果显示，在飞秒强激光脉冲作用下，氢团簇爆炸后所产生的质子能量达几个keV，并且质子能量随着气体背压的升高，即团簇尺寸的增大而逐渐增高。8．飞秒强激光脉冲与团簇喷流相互作用的啁啾脉冲频谱干涉侧量利用惆啾脉冲频谱干涉测量技术，对团簇喷流的粒子数密度以及飞秒强激光与惰性气体团簇相互作用过程中原子的电离过程进行了时间分辨的研究。另外，在飞秒强激光与惰性气体团簇相互作用过程中还观察到非常明显的频谱蓝移和展宽现象。最后，本文对飞秒强激光脉冲与团簇相互作用的理论作了概述，模拟了在飞秒强激光照射下，Arn团簇内的电子温度、电子密度以及团簇的膨胀速度等随时间的变化，并对模拟结果进行了分析。 |
| 英文摘要 | The interaction of femtosecond intense laser pulses with matter is of fundmental scientific interest currently. With the tremendous progress in laser technology, laser pulses with duration of shorter than 10fs and laser intensity on the 1020 W/cm2 scale have been available on a compact table-top system. Cluster is an intermediate state with its size ranging from atom, molecule to bulk solid. The research of the interaction of intense laser pulses with clusters would not only build up a comprehensive micro- and macro-physical picture and the corresponding theoretical model about the interaction of intense field with matter, but also has some potential applications. The major work of this thesis which involves the formation and characterization of large rare gas clusters and hydrogen clusters, the electron impact ionization of rare gas clusters, and the interaction of femtosecond intense laser pulses with rare gas clusters and hydrogen clusters as well is given as follows: 1. Formation and size diagnosis of large rare gas clusters and hydrogen clusters. Large rare gas clusters of Arn, Krn, and Xen and hydrogen clusters were produced in the process of supersonic adiabatic expansion. Rayleigh scattering method is used to diagnose the cluster size. The average cluster size n (atoms per cluster) ranged from 102-106 for rare gas cluster and up to 104 for hydrogen clusters is obtained. A novel two-plateau structure of time-resolved Rayleigh scattering signals of the Krn and Xen clusters is observed for the first time, and three different pulsed valve-nozzle assemblies have been utilized to study the origin of the two-plateau structure and the evolution process of the clusters. 2. Electron impact ionization of large Kr,, and Xen clusters Using an ion gauge detector, the avalanche ionization of large Krn and Xen clusters has been observed for the first time. It is found that the cluster size and cluster density play a critical role in the electron impact ionization of a cluster jet or a cluster beam. 3. Measurement of absorption of rare gas clusters and hydrogen clusters to the energy of femtosecond intense laser pulses The absorption of rare gas clusters and hydrogen clusters to the energy of femtosecond intense laser pulses has been measured. Compared with the low absorption efficiencies of a gas of atoms and molecules (less than 10%), it is demonstrated experimentally that a gas of clusters has much higher absorption efficiency. The absorption efficiencies to the laser energy are as high as 90% and 50% for rare gas clusters and hydrogen clusters, respectively. 4. Production of 1.3 MeV energetic ions from exploding Xe,, clusters irradiated by femtisecond intense laser pulses Using time-of-flight spectrometry, the energy of ions emitted from Xen clusters irradiated by intense femtosecond laser pulses has been measured. The Xe ions with energy up to 1.3 MeV have been observed under optimal experimental conditions. And, it is shown that for Xe clusters, there is an optimal cluster size for average ion energy. 5. Study of the explosion mechanism of Arn clusters irradiated by femtosecond intense laser pulses The explosion mechanism of Arn clusters irradiated by femtosecond intense laser pulses has been studied in a large range of cluster size (n =3x103 -3x 106). It is found that in the size range of n < 3 x 105, the average energies of ions E and the average cluster size n satisfy the relation of E oc n05, Coulomb explosion is believed to be the dominant mechanism of the cluster expansion. Beyond this cluster size, when n > 3 x 105, the average energy of ions increases slowly with the cluster size and gets saturated gradually, and the expansion of clusters is mainly driven by the hydrodynamic force. 6. Characteristics of the angular distribution of ion energy and yield from femtosecond intense laser irradiated Arn clusters The experimental results reveal that the angular distribution of the ions from Arn clusters is anisotropic. The average ion energy and the ion yield in the direction parallel to the laser polarization are 40% and 80% higher than that in the perpendicular direction, respectively. An elliptic micro-plasma sphere model was presented to illustrate the phenomenon. 7. A preliminary study of the interaction of femtosecond intense laser pulses with hydrogen clusters Large size hydrogen clusters (H2)n (w ~104) have been generated by using high gas backing pressure (up to 80 bar) and cryogenic cooling technique. The preliminary experimental results indicate that the energy of protons emitted from the exploding hydrogen clusters is in the order of multi keV, and the proton energy increases as the gas backing pressure increases. 8. Chirped-pulse spectral interferometry of the interaction of femtosecond intense laser pulses with rare gas clusters The number density of a cluster jet, the ionization and the expansion process of clusters irradiated by an intense laser pulse have been studied by employing linearly chirped spectral interferometry. The blueshifting and broadening of the spectrum have also been observed in the laer-cluster interactions. Besides, the theory of the interaction of femtosecond intense laser pulses with clusters has been reviewed. The change with time of the electron temperature and electron density in a cluster which is in a femtosecond intense laser pulse, as well as the expansion velocity of the exploding cluster are simulated. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15564]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 李邵辉. 飞秒强激光脉冲与惰性气体团簇和氢团簇的相互作用研究[D]. 中国科学院上海光学精密机械研究所. 2004. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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