Chemical effects on FKLL Auger spectra in fluorides

Considerable chemical effects have been found on the satellite structures o f F KLL Auger spectra in fluorides recently, which could be important for s urface 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 interp reted on the basis of a new concept, resonant orbital rearrangement. In the present work we study the structure of the Auger satellites induced from r utile-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 i ncreased the peak to background ratio in the spectra significantly. Similar to the alkali fluorides, a satellite has been found in the high kinetic en ergy part of the measured F KLL spectra. From the satellite intensities the fluorescence yield for the doubly ionized states in MgF2 has been determin ed. An inverse proportionality has been found between the satellite/diagram x ray and the corresponding Auger intensity ratios, while the latter ratio s have been found to be proportional to the linewidth of the new Auger sate llites. These observations indicate the resonant nature of the Auger transi tion identified. For determining the energy difference between the molecula r orbitals in resonance, discrete variational X alpha cluster molecular orb ital calculations have been performed and the experimental results have bee n interpreted on the basis of the resonant orbital rearrangement model. Mul tiplet structure calculations for K6F clusters indicate that multiplet spli tting cannot explain the origin of the above satellite peak in the F KLL sp ectrum of solid KF. (C) 2001 American Vacuum Society.