An examination of centrifugal barrier effects in iodine pentafluoride by inner shell electron energy loss spectroscopy

Electron energy loss spectroscopy was used to study the core (I 4d, I 3d, and F Is) level electronic excitation spectra of IF5. The spectra were collected under experimental conditions such that dipole transitions were dominant (high electron impact energy (3 keV) and 0° scattering angle). The spectra were assigned using term value arguments, and by analogy with those of the isoelectronic molecules TeF6 and XeF4. In common with the spectra of TeF6 and XeF4, the spectra of IF5 show features that are consistent with a centrifugal potential-barrier model. In particular, transitions to virtual valence orbitals and to above-edge shape resonance channels are relatively intense, whereas transitions to Rydberg orbitals are, in comparison, very weak or absent. As in the case of TeF6, it was necessary to include atomic 4f orbitals in the molecular orbital basis to adequately account for the continuum resonance features observed in the IF5 spectra. The valence shell electron energy loss spectrum of IF5 from 5 to 35 eV was also obtained.