Probing adsorbate state lifetime with low energy ions

The charge transfer process for an H^- ion backscaterring from the Cs/Cu(111) surface was studied using wave packet propagation (WPP) method. The stabilization of the projectile and adsorbate states by the projected band gap of the Cu(111) surface strengthens the binary collision aspect. The charge fraction of reflected projectiles oscillates as a function of projectile velocity. The negative ion collision spectroscopy in backscattering geometry can probe not only the local electrostatic potentials, but also the lifetimes of adsorbate-induced states.