Access to accurate reference data is a prerequisite in order to translate chemical shifts to an absolute scale for inner-shell ionization energies. Calibration standards for oxygen 1s (O 1s) ionization energies are less well established than, for instance, for carbon 1s. To improve upon this situation, adiabatic and vertical O 1s ionization energies for gaseous carbon dioxide (CO₂) are critically reviewed and used to establish the most accurate values currently available: 541.085(17) and 541.253(17) eV, respectively. Combining these with new precise measurements of shifts in O 1s ionization energies for H₂O, CO, and O₂ allows us to establish equally accurate absolute ionization energies for these molecules as for CO₂. The resulting adiabatic and vertical energies are 539.728(17) and 539.827(17) eV for H₂O, 542.439(17) and 542.495(17) eV for CO, 543.285(17) and 543.294(17) eV for O₂ (⁴Σ final state), and 544.338(17) and 544.423(17) eV for O₂ (²Σ final state). It is proposed that O 1s in CO₂ be adopted as a standard of higher precedence, and that H₂O, CO, and O₂ be used also. The O 1s ionization energies in these molecules occur in the range 540–543 eV. These proposed standards should provide optimal internal calibration for a wide range of oxygen-containing compounds.

获得准确的参考数据是将化学位移转化为内壳电离能的绝对尺度的先决条件。例如，氧 1s (O 1s) 电离能的校准标准不如碳 1s 的校准标准那么完善。为了改善这种情况，对气态二氧化碳 (CO ₂ ) 的绝热和垂直 O 1s 电离能进行了严格审查，并用于确定目前可用的最准确值：分别为 541.085(17) 和 541.253(17) eV。将这些与对 H ₂ O、CO 和 O _{2 的}O 1s 电离能变化的新精确测量相结合，使我们能够为这些分子建立与 CO ₂同样准确的绝对电离能. 将得到的绝热和垂直能量是539.728（17）和539.827（17）eV的用于h ₂ O，542.439（17）和542.495（17）电子伏特为CO，543.285（17）和543.294（17）eV的代表O ₂（⁴ Σ 终态），以及 O ₂ ( ² Σ 终态) 的544.338(17) 和 544.423(17) eV 。建议采用CO ₂中的O 1s作为更高优先级的标准，并且还使用H ₂ O、CO和O ₂。这些分子中的 O 1s 电离能发生在 540-543 eV 的范围内。这些提议的标准应该为各种含氧化合物提供最佳的内部校准。