Clusters in intense XUV pulses: Effects of cluster size on expansion dynamics and ionization
Clusters in intense XUV pulses: Effects of cluster size on expansion dynamics and ionization
复制标题
强 XUV 脉冲中的团簇：团簇尺寸对膨胀动力学和电离的影响
DOI：
10.1103/physreva.83.063201
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发表时间：
2010
影响因子：
2.9
通讯作者：
L. Ramunno
中科院分区：
文献类型：
--
作者：
Edward Ackad;N. Bigaouette;K. Briggs;L. Ramunno
我们研究的Ar{sub 55}-Ar{sub 2057}与强烈的极紫外（XUV）脉冲的相互作用的集群大小的影响，使用我们开发的模型，包括通过碰撞激发电离作为中间步骤。我们发现，这些辐照集群的动力学是占主导地位的碰撞。较大的团簇具有更高的碰撞性，产生更高的电荷状态，并且比较小的团簇更快地这样做。发现通过碰撞产生的更高的电荷态减少了整体光子吸收，因为Ar{sup 2+}和更高的电荷态不再是光可及的。我们称这种机制为碰撞减少的光吸收，它减少了超过30%的有效团簇光吸收截面的Ar{sub 55}和45%的Ar{sub 2057}。电子动能分布的时间演化开始于（大部分）麦克斯韦分布。此外，大团簇的电子速度分布迅速变得各向同性，而较小的团簇保留由光电离产生的固有各向异性。最后，将总电子动能分布在激光空间分布和团簇尺寸对数正态分布上积分，与最近的实验结果进行比较[C。Bostedt等人，物理修订信函100，133401（2008）]，并且发现良好的一致性。
We examine the effect of cluster size on the interaction of Ar{sub 55}-Ar{sub 2057} with intense extreme ultraviolet (XUV) pulses, using a model we developed earlier that includes ionization via collisional excitation as an intermediate step. We find that the dynamics of these irradiated clusters is dominated by collisions. Larger clusters are more highly collisional, produce higher charge states, and do so more rapidly than smaller clusters. Higher charge states produced via collisions are found to reduce the overall photon absorption, since charge states of Ar{sup 2+} and higher are no longer photoaccessible. We call this mechanism collisionally reduced photoabsorption, and it decreases the effective cluster photoabsorption cross section by more than 30% for Ar{sub 55} and 45% for Ar{sub 2057}. The time evolution of the electron kinetic energy distribution begins as a (mostly) Maxwellian distribution. Further, the electron velocity distribution of large clusters quickly become isotropic while smaller clusters retain the inherent anisotropy created by photoionization. Last, the total electron kinetic-energy distribution is integrated over the spatial profile of the laser and the log-normal distribution of cluster size for comparison with a recent experiment [C. Bostedt et al., Phys. Rev. Lett. 100, 133401 (2008)], and good agreement is found.