The paper presents the results of the experimental study of polarization bremsstrahlung profile halfwidth performed on free xenon clusters with various atom numbers. We used 0.7- and 0.3-keV electrons to excite mainly the core and the surface of the clusters, respectively. The halfwidth vs. atom number dependencies were found to be quite different for the 0.7- and 0.3-keV electrons. Analysis of the observed difference allowed us to conclude that the clusters with N = 2000-8000 atoms per cluster (R being about 3-5 nm) consisted of a crystalline fcc core covered by a noncrystalline shell. Our data provide evidence that the surface shell is in the pseudocrystalline state, which is its first observation in rare gas clusters. The pseudocrystalline state observed in metallic clusters is a volume effect, the clusters in this state are structurally unstable and fluctuate continuously between liquid and solid phases.
Asymmetric emission of high energy electrons in the two-dimensional hydrodynamic expansion of large xenon clusters irradiated by intense laser fields
能量谱和角分布已被测量的电子时，释放的$Xe_{150000}$解体后，由强烈的（10 $^{15}-10^{16}$ W cm $^{-2}$）激光脉冲的照射，其持续时间在100-2200 fs的范围内变化。团簇爆炸动力学发生在流体动力学区域。电子发射被发现是出乎意料的不对称，并表现出共振时，激光脉冲宽度为$\sim$ 1 ps。这些结果是合理的扩展的流体动力学模型，也考虑到光场施加的力的偏振电荷上的集群表面上诱导。我们表明，这种电致伸缩力的大小是可比的库仑力和水动力，它表现出共振行为。与早期的理解相反，我们发现低能电子与团簇吸收能量的共振有关。高能电子似乎是由一种不太受共振影响的机制产生的。
