Isomer selective infrared spectroscopy of neutral metal clusters

We report experimental infrared spectra of neutral metal clusters in the gas phase. Multiple photon dissociation of the argon complexes of niobium clusters is used to obtain vibrational spectra in the 80–400 cm–1 region. The observed spectra for Nb9Arn (n = 1–4) are different for different values of n. This is explained by the presence of two isomers of Nb9 that have different affinities towards Ar and the isomer specific infrared spectra are obtained. The structures of the isomers are determined by comparing the observed spectra with the outcome of density-functional theory calculations