The afterglow emission from Nd:YAG-laser-produced microdroplet-tin plasma is investigated, with a focus on analyzing Stark effect phenomena and the dynamical evolution of the plasma. Time- and space-resolved optical imaging spectroscopy is performed on 11 lines from Sn i–iv ions, in the 315–425-nm wavelength range. Stark shift-to-width ratios serve as the basis for unambiguous experimental tests of atomic physics theory predictions. Experiment and theory, where available, are found to be in poor agreement, and are in disagreement regarding the sign of the ratio in several cases. Spectroscopic measurements of the Stark widths in tandem with Saha-Boltzmann fits to Sn i and Sn ii lines, establish the evolution of the local temperature and density of the plasma afterglow, 20–40 ns after the end of the 15-ns-long temporally box-shaped laser pulse. A clear cool-down from $\sim 2$ to 1 eV is observed of the plasma in this time window, having started at $\sim 30$ eV when emitting extreme-ultraviolet (EUV) light. An exponential reduction of the density of the plasma from $\sim {10}^{18}$–${10}^{17}{e}^{-}$ ${\mathrm{cm}}^{-3}$ is observed in this same time window. Our work is relevant for understanding the dynamics of the decaying, expanding plasma in state-of-the-art EUV nanolithography machines.

中文翻译：

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激光产生的锡滴等离子体余辉中的时间和空间分辨光学Stark光谱。

研究了Nd：YAG激光器产生的微滴锡等离子体的余辉发射，重点分析了Stark效应现象和等离子体的动力学演化。时间和空间分辨光学成像光谱是在315-425 nm波长范围内的11条来自Sn  i - iv离子的谱线上进行的。鲜明的宽宽比是原子物理学理论预测的明确实验测试的基础。实验和理论（如果有的话）被发现不一致，并且在某些情况下关于比率的符号不一致。与Saha-Boltzmann串联的Stark宽度的光谱测量适合于Sn  i和Sn  ii在15 ns长的时间盒形激光脉冲结束后20– 40 ns内，用曲线确定等离子体余辉的局部温度和密度的变化。明显的冷静$〜2$ 在此时间窗口内观察到的等离子体的电势为1 eV $〜30$ 发射极端紫外线（EUV）时的eV。等离子体密度的指数下降$〜{10}^{\mathrm{18岁}}$–${10}^{17}{Ë}^{-}$ ${\mathrm{厘米}}^{-3}$在同一时间窗口中观察到。我们的工作与了解最新的EUV纳米光刻机中衰减的，膨胀的等离子体的动力学有关。