We predict the existence of a universal class of ultralong-range Rydberg molecular states whose vibrational spectra form trimmed Rydberg series. A dressed ion-pair model captures the physical origin of these exotic molecules, accurately predicts their properties, and reveals features of ultralong-range Rydberg molecules and heavy Rydberg states with a surprisingly small Rydberg constant. The latter is determined by the small effective charge of the dressed anion, which outweighs the contribution of the molecule’s large reduced mass. This renders these molecules the only known few-body systems to have a Rydberg constant smaller than $R_{\infty }/2$.

中文翻译：

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超长Rydberg分子的离子对平衡态

我们预测存在一类超长距离的里德伯格分子态，其振动光谱形成了修整的里德伯格级数。修饰的离子对模型捕获了这些奇异分子的物理起源，准确地预测了它们的性质，并揭示了超远距离Rydberg分子和重Rydberg态的特征以及令人惊讶的小Rydberg常数。后者是由带负电的阴离子的小有效电荷决定的，该负电荷大于分子的大减少质量的贡献。这使这些分子成为唯一已知的雷德伯格常数小于${\mathrm{[R}}_{\infty }/2$。