QUANTIFICATION OF THE SPECTRAL BROADENING OF THE Ti L-EDGE OF SrTiO3
Keith Gilmore and Eric L. Shirley
Calculations of x-ray absorption spectra are typically limited to obtaining the positions and intensities of spectral features, while simply adding broadening artificially to match experimental results. However, spectral widths hold valuable information on the coupling of the notional excited electronic states with the environment. The 2p53d1 excited state of the Ti4+ ion in SrTiO3 experiences Jahn-Teller coupling to eg distortions of the oxygen cage. Such coupling broadens the electronic transitions by involving a variable number of local eg modes and by mixing the 3d states. We quantify this broadening by solving a model Hamiltonian, taking parameters for the Hamiltonian from first-principles calculations. Comparison of numerical and experimental results indicates that this vibronic coupling accounts for the majority of the broadening observed for the L3-edge, but a lesser fraction of the L2-edge spectral width. Additional broadening of the L2-edge is expected to occur through Coster-Kronig decay.