We present a transition state spectroscopic study of the OH + H₂O reaction using the experimental technique of cryogenic negative ion photoelectron spectroscopy (NIPES). The recorded NIPE spectrum at 193 nm exhibits multiple vibrational progressions that include excitations to the shared H atom antisymmetric stretching mode with an interval of 0.32 eV as well as other progressions, mainly involving the H bending and O···O symmetric stretching modes. The vertical detachment energy (VDE) was measured at 3.53 eV, whereas an upper limit for the adiabatic detachment energy (ADE) was estimated at 2.90 eV. These values are in excellent agreement with the theoretically computed values of 3.51 and 2.87 eV, respectively, obtained at the CCSD(T)/aug-cc-pV5Z level of theory. The recorded NIPE spectrum is in very good agreement when compared to the one recently reported from four-dimensional Franck–Condon simulations, in which a similar spectral profile was predicted. Besides observing the ground state, we identified a charge-transfer excited state in the form of [OH^–(H₂O)⁺] with a relative energy of 1.39 eV, well matching the previous prediction of 1.36 eV.

中文翻译：

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OH ^–（H ₂ O）的低温振动分辨光电子能谱：OH + H ₂ O反应过渡态的多维Franck–Condon模拟结果的确认

我们提出了OH + H ₂的过渡态光谱研究使用低温负离子光电子能谱（NIPES）的实验技术进行O反应。在193 nm处记录的NIPE光谱显示出多个振动级数，其中包括以0.32 eV的间隔激发到共享的H原子反对称拉伸模式的激发以及其他一些进程，主要涉及H弯曲和O···O对称拉伸模式。垂直脱离能（VDE）测得为3.53eV，而绝热脱离能（ADE）的上限估计为2.90eV。这些值分别与在CCSD（T）/ aug-cc-pV5Z理论水平上获得的理论计算值3.51和2.87 eV极为吻合。与最近从四维弗兰克-康登模拟报告的结果相比，所记录的NIPE光谱非常吻合，其中预测了相似的光谱轮廓。除了观察基态，我们还发现了[OH]形式的电荷转移激发态^–（H ₂ O）⁺ ]的相对能量为1.39 eV，与先前的1.36 eV预测非常匹配。