New fine structures resolved at the ELNES Ti-L2,3 edge spectra of anatase and rutile: Comparison between experiment and calculation

Anatase and rutile Ti-L2,3 edge spectra were measured in electron energy loss spectroscopy (EELS) using a transmission electron microscope (TEM) coupled to a CEOS Cs-probe corrector, an omega-type monochromator and an in-column omega-type energy filter fully corrected for 2nd order aberrations. Thanks to the high energy resolution, high electron probe current and high stability achieved under this instrumental configuration, new fine structures, never reported before, were resolved at the L3 band of both rutile and anatase. The data suggest that new peaks also exist in the L2 eg band. The experimental spectra are compared with multichannel multiple scattering (MMS) calculations. Good agreement is found for number, energy position and intensity of the newly resolved spectral features. Up to now, the L3 eg band splitting could not be well described by theory not even through the crystal field multiplet approach. We show that the L3 eg band splitting is due to long range band structure effects, contrary to the usual interpretations in terms of local ligand field or near-neighbour hybridization effects.