Comment on selection-rule effects in electron-energy-loss spectroscopy of Ge and GaAs surfaces

Recent energy-loss and photoemission-partial-yield studies of (spin-orbit-split) d-core to surface-state transitions imply relative transition probabilities for the d52 and d32 components differing from their orbital degeneracies. This has previously been interpreted as implying s character for the unoccupied surface states of GaAs(110). I present an alternative explanation for this effect assuming only p character for these states and a small exchange interaction. © 1976 The American Physical Society.