Heavy-ion–induced shock electrons from sputter-cleaned solid surfaces

Heavy-ion (${\mathrm{C}}^{+}$,${\mathrm{N}}^{+}$,${\mathrm{Kr}}^{+}$)–induced low-energy electron emission (${\mathrm{E}}_{\mathrm{e}}$≤30 eV) has been measured from controlled surfaces of thin solid targets (C,Al,Cu) under ultrahigh-vacuum conditions (p≃${10}^{\mathrm{-}7}$ Pa). The angular distributions of low-energy electrons exhibit prominent structures. In each studied detail these structures agree with the predicted directed emission of ‘‘shock electrons’’ produced by the collective response of the electron plasma of the solid to the distortion of the penetrating heavy ion.