aNeutral silicon clusters doped with first row elements (Si 6 X) have been generated (X = B, C, N, O) and characterized by infrared-ultraviolet (IR-UV) two-photon resonance-enhanced ionization spectroscopy (X = C, O) and quantum chemical calculations (X = Be, B, C, N, O, Si). In the near threshold UV photoionization, the ion signal of specific cluster sizes can be significantly enhanced by resonant excitation with tunable IR light prior to UV irradiation, allowing for the measurement of the IR spectra of Si 7 , Si 6 C, and Si 6 O clusters.Structural assignments are achieved with the help of a global optimization procedure using density functional theory (DFT). The most stable calculated structures show the best agreement between predicted and measured spectra. The dopant atoms in the Si 6 X clusters have a negative net charge and the Si atoms act as electron donors within the clusters. Moreover, the overall structures of the Si 6 X clusters depend strongly on the nature of the dopant atom, i.e., its size and valency. While in some of the Si 6 X clusters one Si atom in Si 7 is simply substituted by the dopant atom (X = Be, B, C), other cases exhibit a completely different geometry (X = N, O). As a general trend, doping of the Si 7 cluster with first-row dopants is predicted to shift the optically allowed electronic transitions into the visible or even near-IR spectral range due to symmetry reduction or the radical character of the doped cluster.

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The infrared spectrum of the disilane cation, Si 2

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Vibrational spectra of Xe-tagged cationic silicon oxide clusters Si(n)O(m)(+) with n = 3-5 and m = n, n ± 1 in the gas phase are obtained by resonant infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory calculations. The Si(n)O(m)(+) clusters are produced in a laser vaporization ion source and Xe complexes are formed after thermalization to 100 K. The clusters are subsequently irradiated with tunable light from an IR free electron laser and changes in the mass distribution yield size-specific IR spectra. The measured IRMPD spectra are compared to calculated linear IR absorption spectra leading to structural assignments. For several clusters, Xe complexation alters the energetic order of the Si(n)O(m)(+) isomers. Common structural motifs include the Si2O2 rhombus, the Si3O2 pentagon, and the Si3O3 hexagon.