We report an intense broadband midinfrared absorption band in the Au10+ cluster in a region in which only molecular vibrations would normally be expected. Observed in the infrared multiple photon dissociation spectra of Au10Ar+, Au10(N2O)+, and Au10(OCS)+, the smooth feature stretches 700-3400 cm-1 (λ=14-2.9 μm). Calculations confirm unusually low-energy allowed electronic excitations consistent with the observed spectra. In Au10(OCS)+, IR absorption throughout the band drives OCS decomposition resulting in CO loss, providing an alternative method of bond activation or breaking.
