Taking advantage of the extreme absolute accuracy, sensitivity, and resolution of noise-immune-cavity-enhanced optical-heterodyne-molecular spectroscopy (NICE-OHMS), a variant of frequency-comb-assisted Lamb-dip saturation-spectroscopy techniques, the rotational quantum-level structure of both nuclear-spin isomers of ${{\text{H}}_2}^{18}\text{O}$ is established with an average accuracy of 2.5 kHz. Altogether, 195 carefully selected rovibrational transitions are probed. The ultrahigh sensitivity of NICE-OHMS permits the observation of lines with room-temperature absorption intensities as low as 10⁻²⁷ cm molecule⁻¹, while the superb resolution enables the detection of a doublet with a separation of only 286(17) kHz. While the NICE-OHMS experiments are performed in the near-infrared window of 7000–7350 cm⁻¹, the lines observed allow the determination of all the pure rotational energies of ${{\text{H}}_2}^{18}\text{O}$ corresponding to J values up to 8, where J is the total rotational quantum number. Both network and quantum theory have been employed to facilitate the measurement campaign and the full exploitation of the lines resolved. For example, to minimize the experimental effort, the transitions targeted for observation were selected via the spectroscopic-network-assisted precision spectroscopy (SNAPS) scheme built upon the extended Ritz principle, the theory of spectroscopic networks, and an underlying dataset of quantum chemical origin. To ensure the overall connection of the ultraprecise rovibrational lines for both nuclear-spin isomers of ${{\text{H}}_2}^{18}\text{O}$, the NICE-OHMS transitions are augmented with six accurate microwave lines taken from the literature. To produce absolute ortho-${{\text{H}}_2}^{18}\text{O}$ energies, the lowest ortho energy is determined to be 23.754 904 61(19) cm⁻¹. A reference, benchmark-quality line list of 1546 transitions, deduced from the ultrahigh-accuracy energy values determined in this study, provides calibration standards for future high-resolution spectroscopic experiments between 0–1250 and 5900–8380 cm⁻¹.

中文翻译：

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基于网络的近红外 Lamb-Dip 实验设计和 H218Oat kHz 精度纯旋转能量的测定

利用噪声免疫腔增强光学外差分子光谱 (NICE-OHMS) 的极端绝对精度、灵敏度和分辨率，这是频率梳辅助兰姆浸饱和光谱技术的一种变体，旋转两种核自旋异构体的量子级结构 ${{\text{H}}_2}^{18}\text{哦}$建立的平均精度为 2.5 kHz。总共探测了 195 个精心挑选的振动跃迁。NICE-OHMS 的超高灵敏度允许观察室温吸收强度低至 10 ^-27 cm 分子^-1的谱线，而卓越的分辨率能够检测分离度仅为 286(17) kHz 的双峰。虽然 NICE-OHMS 实验是在 7000-7350 cm ^-1的近红外窗口中进行的，但观察到的线允许确定所有纯旋转能量${{\text{H}}_2}^{18}\text{哦}$对应于高达 8 的J值，其中J是总旋转量子数。网络和量子理论都被用来促进测量活动和解决线路的充分利用。例如，为了最大限度地减少实验工作，通过基于扩展的 Ritz 原理、光谱网络理论和量子化学起源的基础数据集的光谱网络辅助精密光谱 (SNAPS) 方案来选择用于观察的跃迁. 确保两种核自旋异构体的超精密旋转线的整体连接${{\text{H}}_2}^{18}\text{哦}$，NICE-OHMS 跃迁增加了六个从文献中提取的精确微波谱线。产生绝对正交-${{\text{H}}_2}^{18}\text{哦}$能量，最低正交能量被确定为 23.754 904 61(19) cm ^-1。从本研究中确定的超高精度能量值中推导出的 1546 个转换的基准质量线列表为未来 0–1250 和 5900–8380 cm ^-1之间的高分辨率光谱实验提供校准标准。