Abstract We report the first observation of ion angular distributions originating from electron stimulated desorption of an adsorbed atomic species on a semiconductor surface (ESDIAD). F + is emitted from Si(100)-(2×1) along 4 azimuths corresponding to the principal crystal axes. The most probable F + energy is 2.4 eV. The F + emission angle, α ≈ 36° ± 5° to the surface normal, corresponds closely to the SiF surface bond direction. This F + angular distribution is consistent with F bonding to Si dimers which are in two orthogonal reconstruction on Si(100)-(2×1). The threshold electron energy, V c T = 27.5 ± 1 eV for F + production from the SiF surface species.