[en] When keV to MeV energy ions are inelastically scattered from surfaces at near-grazing angles, the subsequent optical transitions of the projectiles are found to be highly circularly polarized, due to collisional orientation of the excited levels. This orientation increases linearly with ion velocity, at small velocities, and depends on the surface material. The magnitude of the orientation also depends on the concentration and type of gas adsorbed on the surface, and on some details of the absorption process. Measurements of the relative Stokes parameters for several transitions with the same core state, using different projectile charges, provides further information on the ion-surface interaction