Valence band and Zn 3d energy levels in Me₂Zn from photoelectron spectra and pseudopotential ab initio calculations: electric field gradients in gas phase Zn compounds

The He I and X-ray photoelectron spectra of the valence levels and Zn 3d levels in Me₂Zn have been recorded. The orbital ionization potentials are compared with those obtained from our ab initio pseudopotential calculation on Me₂Zn. There is excellent agreement between predicted and observed values for the outer valence orbitals. The Zn 3d level in Me₂Zn in split into five peaks due to the combined effect of spin-orbit splitting and crystal field splitting. The major part of the splitting is due to the asymmetric C⁰₂ crystal field term which transforms like the electric field gradient. The derived C⁰₂ terms for Me₂Zn and ZnCl₂ are -0.0169 ± 0.0007 eV and -0.011 eV respectively. The observed and calculated splitting confirms an electrostatic (rather than a bonding) origin. The C⁰₂ value for Me₂Zn is consistent with that observed recently for Me₂Cd.