Journal of Vacuum Science & Technology A, Vol.19, No.4, 1143-1149, 2001
Chemical effects on FKLL Auger spectra in fluorides
Considerable chemical effects have been found on the satellite structures of F KLL Auger spectra in fluorides recently, which could be important for surface chemical identification and could provide information on the origin and the atomic or molecular character of particular Auger satellite lines. In the case of alkali fluorides unassigned satellites were found and interpreted on the basis of a new concept, resonant orbital rearrangement. In the present work we study the structure of the Auger satellites induced from rutile-type fluorides. F KLL Auger spectra were excited by Al Ka and Cu La x-rays from polycrystalline powder samples of MgF2, ZnF2, NiF2, and CoF2 and measured by a high luminosity electron spectrometer. Excitation by Cu La increased the peak to background ratio in the spectra significantly. Similar to the alkali fluorides, a satellite has been found in the high kinetic energy part of the measured F KLL spectra. From the satellite intensities the fluorescence yield for the doubly ionized states in MgF2 has been determined. An inverse proportionality has been found between the satellite/diagram x ray and the corresponding Auger intensity ratios, while the latter ratios have been found to be proportional to the linewidth of the new Auger satellites. These observations indicate the resonant nature of the Auger transition identified. For determining the energy difference between the molecular orbitals in resonance, discrete variational X alpha cluster molecular orbital calculations have been performed and the experimental results have been interpreted on the basis of the resonant orbital rearrangement model. Multiplet structure calculations for K6F clusters indicate that multiplet splitting cannot explain the origin of the above satellite peak in the F KLL spectrum of solid KF.