RESONANT COHERENT EXCITATION AND IONIZATION OF FAST HYDROGEN-ATOMS INFRONT OF A LIF(001) SURFACE

We have scattered protons with energies ranging from 2 keV to 9 keV fr om a clean and flat LiF(001) surface under a grazing angle of incidenc e and studied the positive ion fractions of scattered projectiles. Fro m a combined variation of projectile energy and azimuthal angle of the target we conclude a pronounced effect on the ion fractions by resona nt coherent excitation and ionization of hydrogen atoms owing to the o scillating electric fields acting on fast projectiles in front of the insulator surface. (C) 1998 Elsevier Science B.V.