Spectroscopy of TaO and TaO2 in Neon and Argon Matrices at 4° and 20°K

Abstract

The TaO and TaO2 molecules vaporizing from tantalum oxide at 2270°K have been trapped in neon and argon matrices at 4° and 20°K and studied spectroscopically in the infrared, visible, and near-ultraviolet regions. TaO spectra exhibit the three electronic transitions observed in the gas and analyzed by Premaswarup and Barrow. The matrix spectra lead to a probable revision of the 4155 Å gas transition, indicating that TaO has a 2Δr ground state. In all, 16 electronic transitions from the X Δ322 level have been distinguished by 18O substitution and most of the upper-state vibrational frequencies determined. Two electronic transitions of TaO2 in a neon matrix occur at 8607 Å (strong) and 6159 Å (weak). The bending frequency in the upper state dominates both of the band systems and indicates that the O–Ta–O angle undergoes a large change in the transitions. The infrared spectrum of TaO2 exhibits two bands, suggesting that the molecule is bent in the ground state. Vibrational frequencies in the ground state are assigned as follows: TaO, 1020 cm−1 (corroborating the gas value); TaO2, v1″=971 cm−1, v2″=?, v3″=912 cm−1. A molecular orbital scheme for each of these molecules is proposed leading to X 2Δr for TaO and X 2B1 for TaO2.