Electron stimulated desorption of F- from condensed NF3: unexpected narrow resonances in the low energy (0–4 eV) desorption yield

Abstract

Electron stimulated desorption of F^- from multilayer films of NF₃ deposited on a cryogenically cooled Au substrate was studied under UHV conditions. By comparison with previous studies on negative ion formation from gas phase NF₃, it is shown that low energy (0–20 eV) desorption is driven by dissociative electron attachment to individual NF₃ molecules at or near the surface. The dominant low energy (0–4 eV) desorption feature shows two energetically separated narrow resonances while the gas phase analogue corresponds to only one broad and unresolved resonance. This broad feature is due to dissociative electron attachment involving two different but energetically overlapping precursor ions. It is shown that the unexpected appearance of the narrow resonances in the desorption yield can be explained by particular energy requirements for ion desorption.