Ionization dynamics of small water clusters: Proton transfer rate

• Published in: Chemical physics Vol. 475; pp. 9 - 13
• Main Authors: Tachikawa, Hiroto, Takada, Tomoya
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 22-08-2016
• Subjects: Ab initio molecular dynamics; Intermediate complex; OH radical; Structural relaxation; Ab initio molecular dynamics; Intermediate complex; Structural relaxation; OH radical
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2016.05.024

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•Reaction rates of proton transfer (PT) processes were determined in small sized water cluster cations.•The rate of PT increased with increasing the cluster size of (H2O)n+ at n=2–5 and reached a limiting value at n=6 and 7.•Dissociation of the OH radical was found in n=4–7.
The surfaces of icy planets and comets are composed of frozen water (H2O), carbon dioxide (CO2), and methane (CH4). These surfaces are irradiated by solar wind and cosmic rays from the interstellar space and they cause ionization of surface molecules. In this report, the effects of ionization of cold water clusters have been investigated using a direct ab initio molecular dynamics (AIMD) method to elucidate the rate of proton transfer (PT) in cations of small water clusters (H2O)n (n=2–7). After ionization of the water clusters, PT occurred in all the cluster cations, and dissociation of the OH radical occurred for n=4–7. The time of PT decreased with increasing the cluster size at n=2–5 and reached a limiting value at n=6 and 7. The mechanism of the PT process in ionized water clusters was discussed based on the theoretical results.