Scientists from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences revealed striking isotopologue dependent photodissociation dynamics of water molecules. The research was published in Journal of Physical Chemistry Letters.
Water, ubiquitous in the universe, absorbs light at all wavelengths in the vacuum ultraviolet region below 190 nm, resulting in fragmentation leading to a hydrogen (H) atom and a hydroxyl (OH) radical. The single bond fission process is an important source of OH radicals in the interstellar medium.
Distinctive isotope dependent dissociation features of water in the interstellar space. (Image by YUAN Kaijun)
The scientists revealed an interesting isotope effect, caused by accidental resonance, which led to different dissociation rates, different dissociation mechanisms, and different product energy disposals following excitation to a common excited state of H2O and D2O.
Such strikingly different fragmentation dynamics of H2O and D2O represented an extreme example of such accidental resonance induced state mixing and might be expected to contribute to the D/H isotope heterogeneity in the Solar System.
This work was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, and the Chemical Dynamics Research Center. (Text by YUAN Kaijun)