Abstract
Low-energy electron-induced reactions in hydrated molecular complexes are important in various fields ranging from the Earth’s environment to radiobiological processes including radiation therapy. Nevertheless, our understanding of the reaction mechanisms in particular in the condensed phase and the role of water in aqueous environments is incomplete. Here we use small hydrogen-bonded pure and mixed dimers of the heterocyclic molecule tetrahydrofuran (THF) and water as models for biochemically relevant systems. For electron-impact-induced ionization of these dimers, a molecular ring-break mechanism is observed, which is absent for the THF monomer. Employing coincident fragment ion mass and electron momentum spectroscopy, and theoretical calculations, we find that ionization of the outermost THF orbital initiates significant rearrangement of the dimer structure increasing the internal energy and leading to THF ring-break. These results demonstrate that the local environment in form of hydrogen-bonded molecules can considerably affect the stability of molecular covalent bonds.
Highlights
Low-energy electron-induced reactions in hydrated molecular complexes are important in various fields ranging from the Earth’s environment to radiobiological processes including radiation therapy
We find that the removal of an electron from the highest occupied molecular orbital (HOMO), which leads to a stable parent ion for the THF monomer, for the dimer initiates a THF ring-break reaction
Two kinds of gas jet targets were employed, a pure THF jet containing about 10–15% dimers THF·THF and a mixed THF water jet with about 4% THF dimers and 4% hydrated C2H4O+ species such as (H2O)·THF dimers
Summary
Low-energy electron-induced reactions in hydrated molecular complexes are important in various fields ranging from the Earth’s environment to radiobiological processes including radiation therapy. Employing coincident fragment ion mass and electron momentum spectroscopy, and theoretical calculations, we find that ionization of the outermost THF orbital initiates significant rearrangement of the dimer structure increasing the internal energy and leading to THF ring-break. These results demonstrate that the local environment in form of hydrogen-bonded molecules can considerably affect the stability of molecular covalent bonds. These observations reveal a so-far unnoticed role of the water environment in enhancing the ring-break of the THF molecule after ionization of the HOMO. This can be important for a better understanding of the reaction mechanisms concerning ionizing radiation in biological matter[3,5]
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