Water acting as a catalyst for electron-driven molecular break-up of tetrahydrofuran

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.

A Complete Cross Section Data Set for Electron Scattering by Pyridine: Modelling Electron Transport in the Energy Range 0–100 eV

“…The differential cross section (DCS) to ionize pyridine has been measured, with a reaction microscope, for 90 eV electron impact energy and different energy loss values, namely 50, 40 and 30 eV. The relevant experimental apparatus was designed and constructed at the MPIK institute [8] and has been recently used to investigate the behavior of different biomolecules [9,10]. The details of this experimental system have been published in these previous studies (see [9,10] and references therein), but will be briefly reiterated in Section 4.1.2.…”

“…The relevant experimental apparatus was designed and constructed at the MPIK institute [8] and has been recently used to investigate the behavior of different biomolecules [9,10]. The details of this experimental system have been published in these previous studies (see [9,10] and references therein), but will be briefly reiterated in Section 4.1.2. This apparatus allows for measurements in coincidence, to provide information about the angular and energy distribution of all the particles involved in the reaction (scattered electron, secondary ejected electron and recoil ion) as well as the fragmentation induced to the target species.…”

“…[1,3]). However, here we also incorporate new electron energy loss distribution functions for the main inelastic processes (vibrational, electronic excitation and ionization), as measured with a standard electron transmission apparatus [7], and double differential ionization cross sections derived from a reaction microscope coincidence analysis [8][9][10]. The reliability of this cross section data set is then evaluated by comparing the simulated electron intensity transmitted through a well-defined molecular density of gaseous pyridine, under strong magnetic field confinement conditions, with that directly measured with an alternative electron transmission apparatus [11].…”

Molecular sunscreen: water protects pyrrole from radiation damage

“…In aqueous solution, the loss of the attached, neutral, ionized, or protonated, water could easily be repaired by the many solvent molecules around. Our analysis of the protection in pyrrole(H 2 O) provides a quantitative analysis of radiation protection and serves as the basis for further investigations of the existing uncertainties [4,13,[36][37][38][39][40][41][42] regarding the role of the solvent environment on the radiation damage of biomolecules.…”

Efficient neutralization of core ionized species in an aqueous environment

“…1 Concerning ionization of hydrated atoms/molecules in particular, unique insights to the effect of neighbouring water molecules have been obtained from recent experiments on pure and doped water clusters. [2][3][4][5][6][7] Generally, molecules neighbouring the primary ionization site influence the electronic decay cascade for example by opening non-local decay pathways, enable the exchange of charge and vibrational energy, and may open or close specific fragmentation channels.…”