Band approach to the excitation-energy dependence of x-ray fluorescence ofTiO2

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-r ay emission features (RXES), which strongly depend on the excitation energy . We are using a band approach in order to discuss the excitation-energy de pendence of Ti L-2,L-3 RXES of TiO2. The RXES process is described as a con volution 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 th e energy interval E-exc +/- Delta E taking into account the rule of k conse rvation. We calculate the curves of restricted joint density of states usin g the full potential linearized muffin-tin orbital method and the results a re found to be in reasonable agreement with the experimental Ti L-2,L-3, RX ES of TiO2 measured at different excitation energies. [S0163-1829(99)12227- 6].