Excitation in low-energy Li+ collisions with cesiated W(110) surfaces: alignment and orientation of the collisionally excited Li(2p) state

The linear and circular polarization of the Li(2p?2s) emission has been measured for Li⁺ collisions with cesiated and oxydized cesiated W(110) surfaces, Cs-W(110) and O/Cs-W(110), at impact energies below 1 keV for an incidence angle of 5 degrees with respect to the surface plane. The cesium coverage has been varied between zero and the saturation coverage at room temperature. Although the excitation of the projectile seems to occur in a binary collision with only one Cs adatom, the presence of the surface influences the total photon yield by Auger deexcitation, and the circular polarization by affecting the energetic separation of the Li(2p) substates close to the surface.