The ${\mathrm{6}\mathrm{p}}^{\mathrm{2}}{{\mathrm{P}}_{1/2}\leftarrow 6\mathrm{s}}^{\mathrm{2}}{\mathrm{S}}_{1/2}$ and ${\mathrm{6}\mathrm{p}}^{\mathrm{2}}{{\mathrm{P}}_{3/2}\leftarrow 6\mathrm{s}}^{\mathrm{2}}{\mathrm{S}}_{1/2}$ transitions (D lines) of gold atoms embedded in superfluid helium nanodroplets have been investigated using resonant two-photon ionization spectroscopy. Both transitions are strongly blue-shifted and broadened due to the repulsive interaction between the Au valence electron and the surrounding helium. The in-droplet D lines are superimposed by the spectral signature of Au atoms relaxed into the metastable ²D states. These features are narrower than the in-droplet D lines and exhibit sharp rising edges that coincide with bare atom transitions. It is concluded that they originate from metastable ²D state AuHe_n exciplexes that have been ejected from the helium droplets during a relaxation process. Interestingly, the mechanism that leads to the formation of these complexes is suppressed for very large helium droplets consisting of about 2 × 10⁶ He atoms, corresponding to a droplet diameter on the order of 50 nm. The assignment of the observed spectral features is supported by ab initio calculations employing a multiconfigurational self-consistent field method and a multi-reference configuration interaction calculation. For large helium droplets doped with Au oligomers, excitation spectra for mass channels corresponding to Au_n with n = 2, 3, 4, 5, 7, and 9 are presented. The mass spectrum reveals even-odd oscillations in the number of Au atoms that constitute the oligomer, which is characteristic for coinage metal clusters. Resonances are observed close by the in-droplet D1 and D2 transitions, and the corresponding peak forms are very similar for different oligomer sizes.

中文翻译：

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氦纳米液滴中金原子和金低聚物的光谱学

这 ${\mathrm{6}\mathrm{p}}^{\mathrm{2个}}{{\mathrm{P}}_{\mathrm{1个}/\mathrm{2个}}\leftarrow 6\mathrm{s}}^{\mathrm{2个}}{\mathrm{小号}}_{\mathrm{1个}/\mathrm{2个}}$ 和 ${\mathrm{6}\mathrm{p}}^{\mathrm{2个}}{{\mathrm{P}}_{3/\mathrm{2个}}\leftarrow 6\mathrm{s}}^{\mathrm{2个}}{\mathrm{小号}}_{\mathrm{1个}/\mathrm{2个}}$使用共振双光子电离光谱技术研究了嵌入超流氦纳米液滴中的金原子的跃迁（D线）。由于金价电子与周围的氦之间的排斥相互作用，两个跃迁都强烈地蓝移并变宽。液滴内的D线与松弛成亚稳² D状态的Au原子的光谱特征叠加。这些特征比液滴中的D线窄，并且具有与裸原子跃迁相符的尖锐上升沿。得出结论，它们起源于亚稳态² D状态AuHe _n在弛豫过程中从氦气小滴中喷出的激基复合物。有趣的是，对于由约2×10 ⁶ He原子组成的非常大的氦滴（对应于约50 nm的滴直径），抑制了导致形成这些络合物的机理。观测光谱特征的分配由采用多配置自洽场方法和多参考配置相互作用计算的从头算来支持。对于掺有Au低聚物的大氦滴，对应于Au _n为n的质量通道的激发光谱= 2、3、4、5、7和9。质谱揭示了构成低聚物的Au原子数量的奇数次振荡，这是造币金属簇的特征。通过滴内D1和D2跃迁可以观察到共振，并且对于不同的低聚物大小，相应的峰形非常相似。