Electron-stimulated desorption of ${\mathrm{F}}^{-}$ and $\mathrm{Cl}{}^{-}$ from submonolayer $\mathrm{CF}{}_2\mathrm{Cl}{}_2$-covered Ru(0001) is strongly affected by coadsorption of polar molecules ( ${\mathrm{H}}_2\mathrm{O}$ and $\mathrm{NH}{}_3$) and nonpolar rare-gas atoms (Xe, Kr, and Ar). Giant anionic enhancements (up to ${10}^2-{10}^4$) are observed for polar molecules, which are several orders of magnitude higher than by nonpolar atoms. The giant enhancements are attributed to enhanced dissociation of $\mathrm{CF}{}_2\mathrm{Cl}{}_2$ by attachment of self-trapped electrons in polar molecules.

• Received 20 January 1999

DOI:https://doi.org/10.1103/PhysRevLett.82.4122