Okumura, M. and Yeh, L. I. and Lee, Y. T. (1988) Infrared spectroscopy of the cluster ions H<sup> + </sup><sub>3</sub>·(H2)n. Journal of Chemical Physics, 88 (1). pp. 79-91. ISSN 0021-9606 http://resolver.caltech.edu/CaltechAUTHORS:OKUjcp88a
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The vibrational spectra of the clusters H<sup> + </sup><sub>3</sub>(H2)n were observed near 4000 cm−1 by vibrational predissociation spectroscopy. Spectra of mass-selected clusters were obtained by trapping the ions in a radio frequency ion trap, exciting vibrational transitions of the cluster ions to predissociating levels, and detecting the fragment ions with a mass spectrometer. Low resolution bands of the solvent H2 stretches were observed for the clusters of one to six H2 coordinated to an H<sup> + </sup><sub>3</sub> ion. The red shift of these vibrations relative to the monomer H2 frequency supported the model of H<sup> + </sup><sub>9</sub> as an H<sup> + </sup><sub>3</sub> with a complete inner solvation shell of three H2, one bound to each corner of the ion. Two additional bands of H<sup> + </sup><sub>5</sub> were observed, one assigned as the H<sup> + </sup><sub>3</sub> symmetric stretch, and the other as a combination or overtone band. High-resolution scans (0.5 and 0.08 cm−1) of H<sup> + </sup><sub>n</sub>, n=5, 7, and 9 yielded no observable rotational structure, a result of either spectral congestion or rapid cluster dissociation. The band contour of the H<sup> + </sup><sub>5</sub> band changed upon cooling the internal degrees of freedom, but the peaks remained featureless. The observed frequencies of H<sup> + </sup><sub>7</sub> and H<sup> + </sup><sub>9</sub> agreed well with ab initio predictions, but those of H<sup> + </sup><sub>5</sub> did not. This deviation is discussed in terms of the large expected anharmonicity of the proton bound dimer H<sup> + </sup><sub>5</sub>.
|Additional Information:||Copyright © 1988 American Institute of Physics. Received 26 August 1987; accepted 16 September 1987. We would like to thank Y. Yamaguchi, J.F. Gaw, and H.F. Schaefer for many stimulating discussions, and for providing us with the results of their calculations prior to publication. This work was supported by the Director, Office of Energy Rersearch, Office of Basic Energy Sciences, Chemical Sciences Division of the U.S. Department of Energy under Contract NO. DE-AC-0376SF00098.|
|Subject Keywords:||HYDROGEN IONS, MOLECULAR IONS, COMPLEXES, ADDUCTS, INFRARED SPECTRA, VIBRATIONAL STATES, PREDISSOCIATION, MOLECULAR CLUSTERS|
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|Deposited On:||17 Apr 2008|
|Last Modified:||26 Dec 2012 09:58|
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