Electronic Structure of the MnO4−, CrO42—, and VO43— Ions from the Metal K X-Ray Spectra

Abstract

New measurements of the K x‐ray emission spectra from the metal atoms in MnO₄⁻, CrO₄^2—, and VO₄^3— ions are presented and discussed in terms of dipole transitions from occupied orbitals to the 1a₁, i.e., the metal 1s vacancy. Observed emission lines are attributed to transitions from the 3t₂ (metal 3p), the 4t₂ (oxygen 2s), and the valence 6t₂ (predominantly oxygen 2pσ) orbitals. Simple theory accounts semiquantitatively for the relative intensities and energy positions of the lines. The K‐absorption spectra of the metal atoms in these ions are considered in conjunction with the emission data. The most prominent absorption peak in each spectrum is attributed to transitions to the 7t₂ orbitals, which apparently consist mainly of metal 4p wavefunctions. Also identified in each spectrum is the absorption edge associated with the onset of photoionization of the K shell. The energy differences between the emission lines and the K‐absorption edge are taken to be the molecular orbital ionization potentials. There is not good agreement between the present deductions from the x‐ray spectra and the results of recent semiempirical calculations of the electronic structure of the MnO₄⁻ ion.