Orientation of Na∗ atoms formed under grazing scattering at an Al surface

A study of the angular momentum orientation of excited Na* 3p atoms by grazing scattering of Na+ ions from an Al surface is presented. The coupled angular mode (CAM) method; previously used for the nonperturbative treatment of dynamic resonant electron-transfer in grazing atom-surface collisions [1,2], is used for the study of this polarization problem. Following the dynamical approach of Brako [3,4] density matrix elements are calculated within the 3p subspace of Na. A pronounced orientation of the orbital angular momentum perpendicular to the scattering plane is obtained. For the first time, a theoretical calculation has yielded a decrease of this atomic orientation with decreasing ion-beam velocities below-0.4 Bohr. Overall agreement of the theoretical results with experimental observations is found.