High-temperature photoelectron spectroscopy. A study of niobium monoxide and tantalum monoxide

Abstract

The He I photoelectron spectra of NbO and TaO have been recorded. In both cases four main bands were observed which can be attributed to ionization of the isolated metal monoxide molecule. Bands associated with other oxides or the metal were not observed.

Assignment of the photoelectron spectra of NbO and TaO was made with the aid of Hartree–Fock–Slater (HFS) calculations and by comparison with the known photoelectron spectrum of VO. The first adiabatic ionization energies of NbO and TaO have been measured as 7.91 ± 0.02 eV and 8.61 ± 0.02 eV, respectively. Suggestions are made to explain the poor agreement between previous mass-spectrometric values for the first ionization energy of each oxide.