Orientation of Atoms Excited by Charged Particles at High Impact Energies

A perturbation-expansion approach is used to examine the sign of the orientation vector as a function of scattering angle and projectile charge. It is shown that for small angles, the sign of the orientation vector is different for oppositely charged projectiles consistent with the prediction of the classical grazing model. At large angles, on the other hand, the orientation vector for oppositely charged projectiles is shown to have the same sign.