Reactions of Laser-Ablated Niobium and Tantalum Atoms with Oxygen Molecules: Infrared Spectra of Niobium and Tantalum Oxide Molecules, Anions, and Cations

Abstract

Laser-ablated niobium and tantalum atoms react with O2 to give MO, MO2, MO2-, and MO2+ products, which are identified from oxygen isotopic substitution on their matrix infrared spectra and from DFT calculations of isotopic frequencies. Annealing allows diffusion and further reaction to form (O2)MO2 complexes, which are characterized by four fundamentals. On the basis of the ν3 vibrational frequencies for the M16O2 and M18O2 isotopic molecules, the metal dioxide valence angles are estimated to be 108 ± 5° for NbO2 and 106 ± 5° for TaO2; the molecular cations have the smaller valence angles 103 ± 5° and 105 ± 5° for NbO2+ and TaO2+, respectively, and the molecular anions are more open with 120 ± 10° valence angles. Evidence is also presented for stable MO3- anion species.