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Infrared Spectra Of Mass-Selected Al+_(Ch4)Nn=1-6clusters, B Poad, C Thompson, E Bieske

Berwyck L. J. Poad

Infrared spectra are recorded for Al⁺–(CH₄)_n n = 1–6 clusters in the CH stretch region (2800–3100 cm⁻¹). The spectra, which are obtained by monitoring photofragmentation in a tandem mass spectrometer, are dominated by a single, narrow band corresponding to the totally symmetric C–H stretching mode of the CH₄ subunits (rendered infrared active through the interaction with the Al⁺ cation). This band shifts progressively to higher wavenumber as the clusters becomes larger, concomitant with a weakening of the intermolecular Al⁺⋯CH₄ bonds. Supporting ab initio calculations for the n = …