The term values of the rotational levels of the first excited vibrational state of the electronic ground state of ${{\text{He}}_2}^{+}$ with a rotational quantum number N⁺ ≤ 13 have been determined with an accuracy of 1.2 × 10⁻³ cm⁻¹ (∼35 MHz) by multichannel-quantum-defect-theory-assisted Rydberg spectroscopy of metastable He₂. Comparison of the experimental term values with the most accurate ab initio results for ${{\text{He}}_2}^{+}$ available in the literature [W.-C. Tung, M. Pavanello, and L. Adamowicz, J. Chem. Phys. 136, 104309 (2012)] reveals inconsistencies between the theoretical and experimental results that increase with increasing rotational quantum numbers. The fundamental vibrational wavenumber of ${{\text{He}}_2}^{+}$ was determined to be 1628.3832(12) cm⁻¹ by fitting effective molecular constants to the obtained term values.

中文翻译：

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分子氦离子（He2 +）的第一激发振动能级的基本振动频率和旋转结构

电子基态的第一激发振动态的旋转能级的项值 ${{\text{他}}_{\mathrm{2个}}}^{+}$通过亚稳态He ₂的多通道量子缺陷理论辅助的Rydberg光谱法确定了旋转量子数N ⁺ ≤13的分子，其准确度为1.2×10 ^-3 cm ^-1（〜35 MHz）。实验术语值与最准确的从头算结果比较${{\text{他}}_{\mathrm{2个}}}^{+}$在文献[W.-C. Tung，M.Pavanello和L.Adamowicz，J.Chem。物理 136，104309（2012）]揭示了这种增加随着旋转量子数的理论和实验结果之间的不一致性。的基本振动波数${{\text{他}}_{\mathrm{2个}}}^{+}$通过使有效分子常数适合于获得的项值，确定为1628.3832（12）cm ^-1。