This paper presents comprehensive spectral measurements and a theoretical analysis of laser-produced germanium (Ge) plasma within the 7.5–17 nm wavelength range, with the measurements being performed using spatiotemporally-resolved emission spectroscopy. We obtained and analyzed the extreme ultraviolet (EUV) spectra and their variations meticulously at various positions adjacent to the target surface. The 3p and 3d excitations of Ge ions spanning from Ge to Ge were calculated using the Cowan configuration interaction codes, with particular emphasis being placed on analysis of the spectral line distributions in the 3d-np, 3d-nf, and 3p-3d, 4s, 4d transition arrays. This analysis indicated the contributions made by these transition arrays to the broadband spectral features that were observed experimentally. By using a steady-state collisional radiation model along with a normalized Boltzmann distribution assumption, we clarified the predominant contributions of the 3d-4p and 3p-3d transitions from the Ge to Ge ions in close proximity to the target surface, along with those from the Ge and Ge ions at greater distances. Furthermore, by combining the results above with a plasma dynamics evolution analysis, we gained insights into how the plasma's transient and nonuniform properties influence the analysis of complex EUV band spectral profiles and examine their implications for spectral diagnostics. These results will be useful for plasma spectral diagnosis and for application to development of pulsed short-wavelength light sources.

中文翻译：

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激光产生的锗等离子体的极紫外宽带光谱特征和时空演化分析


本文介绍了 7.5–17 nm 波长范围内激光产生的锗 (Ge) 等离子体的综合光谱测量和理论分析，测量是使用时空分辨发射光谱进行的。我们获得并分析了目标表面附近各个位置的极紫外 (EUV) 光谱及其变化。使用 Cowan 配置相互作用代码计算从 Ge 到 Ge 的 Ge 离子的 3p 和 3d 激发，特别强调分析 3d-np、3d-nf 和 3p-3d、4s 中的谱线分布, 4d 转换数组。该分析表明这些跃迁阵列对实验观察到的宽带光谱特征做出的贡献。通过使用稳态碰撞辐射模型以及归一化玻尔兹曼分布假设，我们阐明了从靠近目标表面的 Ge 离子到 Ge 离子的 3d-4p 和 3p-3d 跃迁的主要贡献，以及来自Ge 和 Ge 离子的距离更远。此外，通过将上述结果与等离子体动力学演化分析相结合，我们深入了解了等离子体的瞬态和非均匀特性如何影响复杂 EUV 波段光谱轮廓的分析，并检查了它们对光谱诊断的影响。这些结果将有助于等离子体光谱诊断和脉冲短波长光源的开发。