Kinetic-energy shifts in vapour-phase auger-electron spectra of sodium halide molecules

Abstract

The KLL Auger-electron spectrum of sodium and the strongest Auger lines of its halides have been measured from Na, NaF, NaCI, NaBr and NaI in the vapour phase by using electron-impact excitation. The kinetic-energy shifts of the sodium lines in the sodium halides are found to be dominated by molecular relaxation and not by chemical initial-state effects. The chemical shifts have been calculated within the simple point-charge model, and the molecular-relaxation contributions to the shifts have been estimated from differences between semiempirically calculated and measured Auger energies. The molecular-relaxation contribution to the shifts of sodium Auger lines is found to increase strongly on going from NaF to NaI. In contrast, for the halides this relaxation contribution seems to have an almost constant value.