The probability of electron scattering from atomic core states as a function of electron energy, can be extracted from secondary electron yields by differentiation. Fine structure variations above the thresholds for excitation of the vanadium 2p and 2s states are found to extend for several hundred electron volts. The fine structure is altered significantly by reaction of the surface with CO, but is insensitive to long-range order. The structure exhibits periodicities in k, and presumably results from interference of an outgoing spherical wave of a scattered electron with backscattered components from neighboring atoms. The structure therefore appears to be analogous to extended X-ray absorption fine structure (EXAFS). Attempts to extract interatomic spacings by Fourier inversion, however, have been frustrated by multiple scattering effects and other complications. The extreme experimental simplicity provides ample motivation for dealing with these theoretical complexities.
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* This work was supported by the Otlice of Naval Research under grants N00014-75-C-0292,