Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 1: Posters Monday: Clusters, Fullerenes and Nanotubes
MO 1.6: Poster
Montag, 2. April 2001, 12:30–15:00, AT3
Infrared spectra of H2O+-Rgn (n=1-14) complexes (Rg=He, Ne, Ar) — •Otto Dopfer and Doris Roth — Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
IR spectra of the open-shell ionic H2O+-Rg dimers (Rg=He, Ne, Ar) are recorded in the vicinity of the O-H stretch vibrations (ν1, ν3) by means of photodissociation spectroscopy in a tandem mass spectrometer [1-3]. Rotational and vibrational analyses of the spectra clearly show that the Rg ligands form linear ionic hydrogen bonds to the H2O+ cation. In H2O+-Ar [1,2] complexation transforms the symmetric (antisymmetric) O-H stretch of H2O+ into bound and free O-H oscillators. Strong coupling between the bound O-H stretch (ν1) and the intermolecular bond leads to a large red shift in the ν1 frequency and a short lifetime. In contrast, the free O-H stretch (ν3) is only little affected upon Ar complexation, and the resulting long lifetime allows for the resolution of the rotational structure. The spectrum of the Ne complex shows additional splittings which are attributed to exchange tunneling of the two equivalent protons [3]. This interpretation is supported by the spectrum of HDO+-Ne where no splitting is observed. In addition to the H2O+-Rg dimers, spectra of larger H2O+-Arn (n=2-14) clusters are analyzed. The second Ar ligand binds to the second proton of the water cation (C2v). Complexation with further Ar ligands cause smaller frequency shifts owing to weaker intermolecular bonds. Ab initio calculations show good agreement with the experimental data.
[1] O. Dopfer, J. Phys. Chem. A 104, 11693 (2000).
[2] O. Dopfer et al., J. Phys. Chem. A 104, 11702 (2000).
[3] O. Dopfer et al. J. Chem. Phys., submitted.