The extremely broad infrared spectrum of water in the OH stretching region is a manifestation of how profoundly a water molecule is distorted when embedded in its extended hydrogen-bonding network. Many effects contribute to this breadth in solution at room temperature, which raises the question as to what the spectrum of a single OH oscillator would be in the absence of thermal fluctuations and coupling to nearby OH groups. We report the intrinsic spectral responses of isolated OH oscillators embedded in two cold (~20 K), hydrogen-bonded water cages adopted by the Cs+·(HDO)(D2O)19 and D3O+·(HDO)(D2O)19 clusters. Most OH oscillators yield single, isolated features that occur with linewidths that increase approximately linearly with their redshifts. Oscillators near 3,400 cm-1, however, occur with a second feature, which indicates that OH stretch excitation of these molecules drives low-frequency, phonon-type motions of the cage. The excited state lifetimes inferred from the broadening are considered in the context of fluctuations in the local electric fields that are available even at low temperature.

中文翻译：

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在扩展的水网络中捕获固有的，与站点有关的光谱特征和孤立的OH振荡器的寿命。

在OH拉伸区域中，水的红外光谱非常宽泛，这表明水分子嵌入其扩展的氢键网络时会发生多大程度的扭曲。在室温下溶液中的这种广度有许多影响，这引发了一个问题，即在没有热波动且不耦合至附近的OH基团的情况下，单个OH振荡器的光谱将是什么。我们报告了隔离的OH振荡器的固有光谱响应，该振荡器嵌入两个由Cs +·（HDO）（D2O）19和D3O +·（HDO）（D2O）19簇采用的冷的（〜20 K）氢键水笼中。大多数OH振荡器会产生单个孤立的特征，这些特征的线宽随其红移近似线性增加。但是，在3,400 cm-1附近的振荡器具有第二个特征，这表明这些分子的OH拉伸激发驱动了笼子的低频声子型运动。由扩展推导的激发态寿命是在局部电场的波动范围内考虑的，该局部电场甚至在低温下也可以使用。