Three energetically close pairs of vibrational states in glycolic acid are investigated by Raman spectroscopy in a supersonic jet to provide challenging benchmarks for vibrational and electronic structure theory and to solve some open issues in this prototypical hydroxy acid. The alcoholic OH stretching fundamental is located only 8 cm^–1 below the acidic OH stretch at 3586 cm^–1, much less shifted than predicted by previous anharmonic calculations and by experimental analogy to a fluorene derivative. This and further near-degeneracies in the CH and C=O stretching region are used to assess the predictive power of an exploratory set of quantum chemical calculations including anharmonic VPT2 corrections.

中文翻译：

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乙醇酸作为振动非谐性基准。

在超音速喷气机中通过拉曼光谱研究了乙醇酸中三个能量上接近的振动状态对，为振动和电子结构理论提供了具有挑战性的基准，并解决了该原型羟基酸中的一些未解决问题。醇OH伸缩基本仅位于8厘米^-1酸性OH拉伸低于3586厘米^-1，更不用说偏移比由前面的非调谐计算预测和通过实验类似于芴衍生物。CH和C = O拉伸区域中的这种以及进一步的近简并性被用来评估一组探索性的量子化学计算（包括非谐VPT2校正）的预测能力。