Auger decay mechanism in photon-stimulated desorption from sodium fluoride

Abstract

Photon-stimulated desorption of ${\mathrm{Na}}^{+}$ and ${\mathrm{F}}^{+}$ occurs from a NaF(100) cleaved surface upon $\mathrm{Na}(1s)$ excitation. These measurements represent the first observation of metal-cation desorption following metal-cation---core excitation. In agreement with the Auger decay model of desorption, both sodium and fluorine positive-ion yields (versus photon energy) are similar to total electron yield in the vicinity of the Na $K$ edge, except for a pre-edge peak observed predominantly in ${\mathrm{Na}}^{+}$ desorption. Intra-atomic Auger decay of the $\mathrm{Na}(1s)$ core hole followed by charge transfer from adjacent halogens is shown to initiate desorption. The resulting neutral or positively charged halogens provide the driving force for desorption of sodium ions from the surface. Expressions are developed for the maximal energy available to the desorbing ${\mathrm{Na}}^{+}$ or ${\mathrm{F}}^{+}$ ions.