Band approach to the excitation-energy dependence of x-ray fluorescence of TiO2

Excitation-energy dependence of Ti L-2,L-3 soft x-ray emission spectra (XES) of a TiO2 single crystal is measured near Ti 2p threshold using tuneable synchrotron radiation at excitation energies E-exc = 458.2-476.9 eV. It is found that the emission spectra exhibit normal soft x-ray emission features, which do not change with excitation energy and inelastic and resonant x-ray emission features (RXES), which strongly depend on the excitation energy. We are using a band approach in order to discuss the excitation-energy dependence of Ti L-2,L-3 RXES of TiO2. The RXES process is described as a convolution of occupied and unoccupied d states in the intermediate and final states. In this procedure the d states are limited to those which lie in the energy interval E-exc +/- Delta E taking into account the rule of k conservation. We calculate the curves of restricted joint density of states using the full potential linearized muffin-tin orbital method and the results are found to be in reasonable agreement with the experimental Ti L-2,L-3, RXES of TiO2 measured at different excitation energies. [S0163-1829(99)12227-6].