Infrared spectroscopy of the cluster ions H/sup +//sub 3/ x(H/sub 2/)/sub n/
The vibrational spectra of the clusters H/sup +//sub 3/(H/sub 2/)/sub n/ were observed near 4000 cm/sup -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 H/sub 2/ stretches were observed for the clusters of one to six H/sub 2/ coordinated to an H/sup +//sub 3/ ion. The red shift of these vibrations relative to the monomer H/sub 2/ frequency supported the model of H/sup +//sub 9/ as an H/sup +//sub 3/ with a complete inner solvation shell of three H/sub 2/, one bound to each corner of the ion. Two additional bands of H/sup +//sub 5/ were observed, one assigned as the H/sup +//sub 3/ symmetric stretch, and the other as a combination or overtone band. High-resolution scans (0.5 and 0.08 cm/sup -1/) of H/sup +//sub n/, 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 +//sub 5/ band changed upon cooling the internal degrees of freedom, but the peaks remained featureless. The observed frequencies of H/sup +//sub 7/ and H/sup +//sub 9/ agreed well with ab initio predictions, but those of H/sup +//sub 5/ did not. This deviation is discussed in terms of the large expected anharmonicity of the proton bound dimer H/sup +//sub 5/.
- Research Organization:
- Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5596258
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 88:1; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ADDUCTS
CHARGED PARTICLES
COMPLEXES
DISSOCIATION
ENERGY LEVELS
EXCITED STATES
HYDROGEN IONS
INFRARED SPECTRA
IONS
MOLECULAR IONS
PREDISSOCIATION
SPECTRA
VIBRATIONAL STATES