Identification, structure, and spectroscopy of neutral vanadium oxide clusters

Neutral vanadium oxide clusters are studied by photoionization time-of-flight (TOP) mass spectroscopy, electronic spectroscopy, and density functional theory (DFT) calculations. Mass spectra of vanadium oxide clusters are observed by photoionization with lasers of three different wavelengths: 118, 193, and 355 nm. Mechanisms of 118 nm single photon ionization and 193 and 355 nm multiphoton ionization/fragmentation of vanadium oxide clusters are discussed on the basis of observed mass spectral patterns and line widths of the mass spectral features. Only the 118 nm laser light can ionize vanadium oxide neutral species by single photon ionization without fragmentation. The stable vanadium oxide neutral clusters under saturated oxygen growth conditions are found to be of the form (VO ₂) _x(V ₂O ₅) _y. Structures of the first few members of this series of clusters are determined through high level DFT calculations. Fragmentation of this series of clusters through 355 and 193 nm multiphoton ionization processes is discussed in light of these calculated structures. The B ²B ₂←X̃ ²A ₁ transition is observed for the VO ₂ neutral species, and v ₁ and v ₂ vibrations are assigned for both electronic states. From this spectrum, the VO ₂ rotational and vibrational temperatures are found to be ∼50 and ∼700 K, respectively.