State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, 116023, Dalian, China.
Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, 230026, Hefei, Anhui, People's Republic of China.
Nat Commun. 2019 Mar 19;10(1):1250. doi: 10.1038/s41467-019-09176-z.
Hydroxyl radicals (OH) play a central role in the interstellar medium. Here, we observe highly rotationally excited OH radicals with energies above the bond dissociation energy, termed OH "super rotors", from the vacuum ultraviolet photodissociation of water. The most highly excited OH(X) super rotors identified at 115.2 nm photolysis have an internal energy of 4.86 eV. A striking enhancement in the yield of vibrationally-excited OH super rotors is detected when exciting the bending vibration of the water molecule. Theoretical analysis shows that bending excitation enhances the probability of non-adiabatic coupling between the [Formula: see text] and [Formula: see text] states of water at collinear O-H-H geometries following fast internal conversion from the initially excited [Formula: see text] state. The present study illustrates a route to produce extremely rotationally excited OH(X) radicals from vacuum ultraviolet water photolysis, which may be related to the production of the highly rotationally excited OH(X) radicals observed in the interstellar medium.
羟基自由基 (OH) 在星际介质中起着核心作用。在这里，我们通过水的真空紫外光解观察到了能量超过键离解能的高度旋转激发的 OH 自由基，称为 OH“超转子”。在 115.2nm 光解下鉴定出的最高度激发的 OH(X) 超转子具有 4.86eV 的内部能量。当激发水分子的弯曲振动时，检测到振动激发的 OH 超转子产率的显著增强。理论分析表明，弯曲激发增强了在快速内转换后，沿共线 O-H-H 几何形状，从初始激发的 [Formula: see text] 态到 [Formula: see text] 和 [Formula: see text] 态之间的非绝热耦合的概率。本研究说明了一种从真空紫外光解水中产生高度旋转激发的 OH(X) 自由基的途径，这可能与星际介质中观察到的高度旋转激发的 OH(X) 自由基的产生有关。
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