Theoretical investigation of the ultrafast dissociation of core-ionized water and uracil molecules immersed in liquid water

Abstract

We present a series of ab initio density functional based calculations of the fragmentation dynamics of core-ionized biomolecules. The computations are performed for pure liquid water, aqueous andisolated Uracil. Core ionization is described by replacing the 1s2 pseudopotential of one atom of the target molecule (C, N or O) with a pseudopotential for a 1s1 core-hole state. Our results predict that thedissociation of core-ionized water molecules may be reached during the lifetime of inner-shell vacancy (less than 10 fs), leading to OH bond breakage as a primary outcome. We also observe a second fragmentationchannel in which total Coulomb explosion of the ionized water molecule occurs. Fragmentation pathways are found similar for pure water or when the water molecule is in the primary hydration shell of the uracilmolecule. In the latter case, the proton may be transferred towards the uracil oxygen atoms. When the core hole is located on the uracil molecule, ultrafast dissociation is only observed in the aqueous environment and for nitrogen-K vacancies, resulting in proton transfers towards the hydrogen-bonded water molecule.