Threshold for Potential Sputtering of LiF

We have measured total sputtering yields for impact of slow ( $\le 100\mathrm{eV}$) singly and doubly charged ions on LiF. The minimum potential energy necessary to induce potential sputtering (PS) from LiF was determined to be about 10 eV. This threshold coincides with the energy necessary to produce a cold hole in the valence band of LiF by resonant neutralization. This allows the first unambiguous identification of PS induced by cold holes. Further stepwise increase of the sputtering yield with higher projectile potential energies provides evidence for additional defect-mediated sputtering mechanisms operative in alkali halides.