We use an electrostatic model to study the average kinetic energy of ions ejected from the pure Coulomb explosions of methane clusters (CA4)n (light atom A=H and D). It is found that the ratio of the average kinetic energy of the ions to their initial average electrostatic potential energy is irrelevant to the cluster size. This finding implies that as long as the ratio is given, the average kinetic energies of the ions can be simply estimated from their initial average electrostatic potential energies, rather than from the time-consuming simulations. The ratios for the different charge states of carbon ions are presented.

A simplified Coulomb explosion model is presented for the analysis of the explosion dynamics of hydrogen clusters driven by an ultrashort intense laser pulse. The scaling of the proton kinetic energy with cluster size has been studied in detail based on this model. It is found that the maximum kinetic energy the protons acquire in the laser-cluster interaction rises to a peak and then decreases slightly as the cluster size increases, which can be explained very well by investigating the temporal evolution of outer ionization rate of different-size clusters. It is also indicated that there exists an optimum cluster size to maximize the proton energy for given laser parameters. Moreover, taking the cluster-size distribution as a log-normal function distribution into account, the maximum proton energy increases sharply with the cluster size and then levels off before beginning to fall slowly. The inclusion of a cluster-size distribution into the simulations considerably improves the fit with experimental data. These discussions are useful for the optimum-match determination of laser-cluster parameters to obtain the maximum proton energy in experiments.

报道了飞秒强激光脉冲(60 fs,790 nm,2×1016 W/cm2)与纳米尺寸的氢团簇(半径rc约为1～3 nm)相互作用,产生的最大质子能量Emax对于团簇半径rc相关性的实验研究结果。从激光-氢团簇相互作用产生的质子的飞行时间谱测量以及团簇尺寸的瑞利散射诊断结果,得到Emax与r2c成线性正比关系,比例系数为075,与报道的理论模拟结果一致,表明氢团簇发生纯库仑爆炸。实验结果同时提示,进一步的理论模拟应考虑气体喷流中团簇的尺寸分布。

通过数值求解三维电场传播方程,理论模拟了飞秒强激光脉冲(50 fs,1016w/cm2)在氩气和中等尺寸氩团簇中的传播效应.结果表明,飞秒强激光脉冲经氩气传播将发生频谱蓝移展宽和光束发散;而经中等尺寸氩团簇传播,则存在一定程度的自聚焦效应.

运用经典粒子动力学模拟方法,研究了飞秒强激光脉冲(1015～1016 W/cm2)与正二十面体构型氢原子团簇H13,H55,H147和H309的相互作用。通过模拟分析团簇的膨胀过程,发现团簇的膨胀是各向同性的,团簇的膨胀尺度R(t)/R(0)随团簇尺寸的增大而减小,即团簇尺寸愈大,与激光相互作用后膨胀碎解过程愈慢。研究结果表明,随着团簇中原子数目的增多,团簇库仑爆炸后所产生的离子的动能相应增大。由于正二十面体的对称壳层结构,离子动能分布具有尖峰结构。团簇库仑爆炸后离子的最大动能Emax与团簇库仑爆炸前的尺寸的平方成正比。且Emax随激光光强I增加而增大。但是当I增大到一定值Is时,Emax将出现饱和,这是因为I的增强已经不再改变团簇内原子的电离状态。随着团簇尺寸的增大,激光光强饱和值和离子能量将会继续提高。

用激光蒸发石墨靶棒，脉冲载气(carriergas)冷却的方法产生碳团簇，由飞行时间质谱仪测得碳团簇负离子的飞行时间质谱。通过对质谱的研究，揭示出随着尺寸的增长，碳团簇的结构由环状为主变为由笼状占大多数。进一步讨论了脉冲气体与蒸发激光的强弱对实验结果的影响。

超短强激光与大尺寸原子团簇的相互作用研究是90年代开拓的一个崭新的强激光与物质相互作用的研究领域.由于大尺寸原子团簇兼有气体的低平均密度孤立体系和固体的高局域密度的独特双重特性,因而相对于固体靶和气体靶,大尺寸原子团簇靶对入射激光具有更高的能量吸收率,能够产生温度更高的等离子体,释放出更强的X射线和能量更高的电子、离子.……

用传输矩阵法从理论上计算了取样光纤布拉格光栅的反射(传输)谱特性, 提出了几种提高其谱特性的调制方案。 用取样掩模版一次成栅的方法首次获得了波长间隔为0.8 nm和1.6 nm的取样光纤布拉格光栅。

瑞利散射法的优点是实验易行，对于团簇是非破坏性的。利用这种方法，A. J. Bell等人测出了尺寸在150～4000的氩团簇。R. Klingelhofer测量了瑞利散射信号强度同散射角的依赖关系，推断出氢团簇尺寸分布。T. Ditmire等在散射角固定不变(θ＝90)的情况下，测量散射信号同气体滞止压强P0或温度T0的关系，从而推断团簇的尺寸。H2在79 K及Ar在293 K，瑞利散射信号同压强的标定关系为≈P3.80和P3.60，分别测得最大团簇尺寸Nc≈690(H2)和1160 (Ar)。对于Ar在147 K，背景压强低于35 kTorr时，SRS∝P3.80，而在更高的压强下，SRS∝P4.30，所产生团簇最大尺寸约为3.5×104。