M/sub 4,5/N/sub 4,5/X Auger line shapes of La compounds from one-step model calculations

The x-ray-excited M/sub 4,5/N/sub 4,5/X (X = O1, O/sub 2,3/, and N/sub 6,7/) Auger spectra of La metal, La2O3, and LaF3 are calculated by use of the one-step model for which the decoupling of Auger decay and photoemission processes are not assumed. It is shown that the line shape of the individual Auger transition for La metal is quite different from those of LaF3 and La2O3 because of the interference effect between photoemission and the Auger decay arising from the N/sub 67/VV extra relaxation mechanism, although this difference is mostly smeared out in the experimental Auger spectra due to multiplets and other broadening effects. The well screened and poorly screened Auger final-state peaks are separated by the energy difference ΔU = U/sub f//sub α/+U/sub f//sub β/-U/sub fc/, where U/sub f//sub c/, U/sub f//sub α/, and U/sub f//sub β/ are Coulomb attraction energies between a 4f electron and core holes c, α, and β involved in the cαβ Auger process. From the comparison of the calculated total Auger line shape with the experimental one, we can estimate ΔU 5 eV for La compounds, and this makes the two-step model a good approximation for calculating relative intensities of various Auger peaks