Resonant Coherent Excitation of Fast Hydrogen Atoms in Front of a LiF(001) Surface

Abstract

We have scattered protons and hydrogen atoms with energies of some keV from a LiF(001) surface under a grazing angle of incidence. From the intensity of Lyman-\ensuremath{\alpha} radiation (transition from $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ to $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1,\ensuremath{\lambda}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}121.6\mathrm{nm}$) as a function of projectile energy for different azimuthal orientations of the crystal surface, we find clear evidence for a resonant coherent excitation of $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ states of hydrogen atoms in the oscillating electric field in front of the insulator surface.