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Abstract

The gas-phase infrared spectroscopy of V₄O₁₀⁺ produced by laser vaporization has been studied in the spectral region from 7 to 16 µm. Mass-selected V₄O₁₀⁺cations were stored in a helium filled radio frequency hexadecapole ion trap and excited using tunable infrared radiation from a free electron laser. The photodissociation spectrum was recorded by monitoring the V₄O₈⁺ yield (O₂ loss) as a function of the excitation wavelength. Two absorption bands at 842 and 1032 cm⁻¹ are observed, which are assigned to resonant excitation of the antisymmetric V–O–V stretching and VO stretching vibrations, respectively. Comparison to recent theoretical and experimental studies indicate that the absorbing species consists of a V₄O₈⁺ ionic core weakly bound to an oxygen molecule.