INFRARED SPECTRA OF $NH_{3}^{+} -Ar_{n}$ (n=1-6) COMPLEXES (n=1-6)
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Date
2000
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Ohio State University
Abstract
Intermolecular forces and microsolvation processes in $NH_{3}^{+} -Ar_{n}$ complexes (n=1-6) are studied by infrared photodissociation spectroscopy in a tandem mass spectrometer. Analysis of the rovibrational structure yields a proton bound dimer equilibrium structure with $C_{2v}$ symmetry. Observed tunnelling splittings are attributed to hindered internal rotation of the planar $NH_{3}^{+}$ cation within the dimer. Systematic frequency shifts observed in the spectra of larger clusters provide a detailed picture of the cluster growth. The first three Ar ligands form equivalent linear proton bonds, leading to highly symmetric cluster structures with $C_{2v}$ or $D_{3h}$ symmetry. The next two Ar atoms bind to the $2p_{z}$ orbital of the central N atom on opposit e sites of the $C_{3}$ axis, leading to structures with $C_{3v}$ and $D_{3h}$ symmetry. Ab initio calculations support the interpretation of the experimental data.
Description
Author Institution: Institut f\""ur Physikalische Chemie, Universit\""at Basel