LIGAND-FIELD SPLITTING ON THE XE 4D CORE LEVELS IN XEFX (X = 2, 4, 6) COMPOUNDS FROM HIGH-RESOLUTION GAS-PHASE PHOTOELECTRON-SPECTRA - THE STRUCTURE OF XEF6

Using monochromatized synchrotron radiation, high-resolution (total line widths of approximately 0.2 eV) Xe 4d photoelectron spectra are reported for the three xenon fluorides, XeFx (x = 2, 4, 6). The splitting of the Xe 4d3/2 and 4d3/2 core levels is due to the ligand field splitting on the Xe 4d ion state. The splitting is due to the asymmetric C2(0) crystal field term, which transforms like the electric field gradient as normally measured by Mossbauer spectroscopy or NQR. The appreciable ligand field splitting in XeF6 shows immediately that XeF6 is considerably distorted from octahedral symmetry. We have derived the bond angles for the C3-nu XeF6 structure using the C2(0) for XeF6 and an additive treatment which has been shown to work well for e2qQ values, giving estimates of theta-1,2.3 = 50 +/- 2-degrees and theta-4,5,6 = 76 +/- 4-degrees. These values are in good agreement with the latest theoretical determinations for these angles.