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Title: Communication: Electron impact ionization of binary H2O∕X clusters in helium nanodroplets: an ab initio perspective.
Authors: Shepperson, Benjamin
Liu, Jun
Ellis, Andrew M.
Yang, Shengfu
First Published: 30-Nov-2012
Publisher: American Institute of Physics (AIP)
Citation: Journal of Chemical Physics, 2012, 137 (20), pp. 1102-5
Abstract: In a recent experiment (H2O)n/Xm binary clusters (where X = Ar, N2, CO, CO2, and several other molecules) were formed in superfluid helium nanodroplets and investigated by electron impact mass spectrometry [Liu et al., Phys. Chem. Chem. Phys. 13, 13920 (2011)10.1039/c1cp20653b]. The addition of dopant X was found to affect the branching ratio between H3O+(H2O)n and (H2O)+n+2 formation. Specifically, the addition of CO increased the proportion of protonated water cluster ions, whereas dopants such as Ar, N2, and CO2, had the opposite effect. In this work ab initio calculations have been performed on [X(H2O)2]+ ions, where X = Ar, N2, CO, and CO2, to try and explain this distinct behavior. CO is found to be unique in that it forms a HOCO-H3O+ unit in the most stable cationic complexes where the binding between HO and CO is stronger than that between H3O+ and OH. Thus, on purely energetic grounds, loss of HOCO rather than CO should be the preferred fragmentation process. No comparable chemistry occurs when X = Ar, N2, or CO2 and so the co-dopant requires less energy to depart than OH. The calculations therefore account for the experimental observations and provide evidence that HOCO formation is induced in helium droplets containing (H2O)n clusters and co-doped with CO when subject to electron impact ionization.
DOI Link: 10.1063/1.4769810
ISSN: 0021-9606
eISSN: 1089-7690
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2012 American Institute of Physics. Deposited with reference to the publisher's archiving policy available on the SHERPA/RoMEO website. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Chemical Physics, 2012, 137 (20), pp. 1102-5 and may be found at
Appears in Collections:Published Articles, Dept. of Chemistry

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