@article {C0SC00604A,
	title = {Structural trends of ionized water networks: Infrared spectroscopy of water cluster radical cations (H2O)n+ (n = 3-11)},
	journal = {Chem. Sci.},
	volume = {2},
	year = {2011},
	note = {n/a},
	pages = {868-876},
	publisher = {The Royal Society of Chemistry},
	abstract = {<p>The nature of water networks exposed to ionizing radiation is important in various radiation-related chemistry and biology. To understand structural evolution of ionized water networks at the molecular level{,} we report here infrared spectra of water cluster radical cations (H2O)n+ (n = 3 - 11) in the gas phase. Spectral features of free OH stretch modes are quite similar to those of protonated water clusters H+(H2O)n{,} of which the hydrogen-bond network structures have been revealed. In addition{,} we observed an extra band attributed to the stretch of an OH radical in (H2O)n+. These results indicate that nominal (H2O)n+ should be regarded as H+(H2O)n-1(OH) motifs having similar network shapes to those of H+(H2O)n. We also analyzed hydrogen-bonded OH stretch bands and found that hydrogen-bond strength is a key factor to determine the position of the OH radical relative to the protonated site (H3O+/H5O2+). Because an OH radical is a weaker hydrogen bond acceptor than water{,} the first solvation shell of the protonated site is preferentially filled with water. As a result{,} the OH radical is separated from the protonated (charged) site by at least one water molecule in n [greater-than-or-equal] 5 clusters. This result shows the instability of the H3O+-OH ion-radical contact pair in water networks{,} and implies the higher mobility of the OH radical due to its release from the charged site. Observed structural preferences are confirmed both in cold and warm cluster ion sources.</p>
},
	doi = {10.1039/C0SC00604A},
	url = {http://dx.doi.org/10.1039/C0SC00604A},
	author = {Mizuse, Kenta and Jer-Lai Kuo and Fujii, Asuka}
}
