Reactions associated with ionization in water: A direct ab initio dynamics study of ionization in (H 2O) 17

A. Furuhama, Michel Dupuis, K. Hirao

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Quasiclassical ab initio simulations of the ionization dynamics in a (H2 O)17 cluster, the first water cluster that includes a fourfold coordinated (internally solvated) water molecule, have been carried out to obtain a detailed picture of the elementary processes and energy redistribution induced by ionization in a model of aqueous water. General features observable from the simulations are the following: (i) well within 100 fs following the ionization, one or more proton transfers are seen to take place from the "ionized molecule" to neighboring molecules and beyond, forming a hydronium ion and a hydroxyl radical; (ii) two water molecules close to the ionized water molecule play an important role in the reaction, in what we term a "reactive trimer." The reaction time is gated by the encounter of the ionized water molecule with these two neighboring molecules, and this occurs anytime between 10 and 50 fs after the ionization. The distances of approach between the ionized molecule and the neighboring molecules indeed display best the time characteristics of the transfer of a proton, and thus of the formation of a hydronium ion and a OH radical. These findings are consistent with those for smaller cyclic clusters, albeit the dynamics of the proton transfer displays more varieties in the larger cluster than in the small cyclic clusters. We used a partitioning scheme for the kinetic energy in the (H2 O)17 system that distinguishes between the reactive trimer and the surrounding "medium." The analysis of the simulations indicates that the kinetic energy of the surrounding medium increases markedly right after the event of ionization, a manifestation of the local heating of the medium. The increase in kinetic energy is consistent with a reorganization of the surrounding medium, electrostatically forced in a very short time by the water cation and in a longer time by the formation of the hydronium ion.

Original languageEnglish
Article number164310
JournalJournal of Chemical Physics
Volume124
Issue number16
DOIs
Publication statusPublished - 2006

Fingerprint

Ionization
ionization
Molecules
Water
water
hydronium ions
molecules
Kinetic energy
Proton transfer
kinetic energy
trimers
protons
simulation
hydroxyl radicals
reaction time
encounters
Hydroxyl Radical
Cations
Protons
Heating

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Reactions associated with ionization in water : A direct ab initio dynamics study of ionization in (H 2O) 17. / Furuhama, A.; Dupuis, Michel; Hirao, K.

In: Journal of Chemical Physics, Vol. 124, No. 16, 164310, 2006.

Research output: Contribution to journalArticle

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