Ablation plumes caused by short-pulse laser irradiation provide conditions which are well suited to the formation of nanoclusters. The high saturation ratios and presence of ionization lead to extraordinarily hi oh nucleation rates and small critical radii. We have explored the homogeneous nucleation and heterogeneous growth of condensates from Si targets expanding into a low-pressure He ambient using a Nd:YAG laser with a pulse length of 8 ns, wavelength of 532 nm and intensities in the range of 5 X 10~7 -5 X 10~9 W cm~(-2). Clusters in the range of 5-50 nm have been produced. In the highly dynamic, non-linear regime of short-pulse laser-matter interactions, plume evolution and condensation processes are strongly coupled and difficult to predict accurately from modelling alone. Both numerical predictions and experimental results were used to quantify the competing effects of ionization and supersaturation. The results suggest a dominant influence of ionization for nearly all intensities above the ablation threshold.
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机译：由短脉冲激光辐照引起的烧蚀羽流提供了非常适合形成纳米团簇的条件。高饱和比和电离的存在会导致极高的成核速率和较小的临界半径。我们使用Nd：YAG激光，脉冲长度为8 ns，波长为532 nm，强度范围为5 X 10〜的Nd：YAG激光器探索了从Si目标扩展到低压He环境中的凝结物的均匀成核和非均质生长7 -5 X 10〜9 W cm〜（-2）已经产生了5-50nm范围内的簇。在短脉冲激光-物质相互作用的高度动态，非线性状态下，羽状流演化和凝结过程紧密耦合，并且难以单独通过建模准确预测。数值预测和实验结果均用于量化电离和过饱和的竞争效应。结果表明，对于高于烧蚀阈值的几乎所有强度，电离的主要影响。
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