POLARIZED-LIGHT EMISSION IN KEV HE2++NA(3S) COLLISIONS

We investigated l and m-distributions of He II (n = 4) states formed d uring 2-13.3 keV amu(-1) He2+ + Na(3s) collisions by measuring profile s and the linear polarization of the He II (4 --> 3) emission. We foun d that at these energies capture into He+(4f) dominates over capture i nto other He+(4l) states. Over the indicated energy range the polariza tion of the He-4 II (4 --> 3) photon emission increases from 0.2 to 0. 3 indicating a strong alignment of the captured projectile charge clou d along the internuclear axis. Due to the non-zero nuclear spin the po larization is up to 10% lower when using He-3(2+) projectiles instead of He-4(2+). Classical trajectory Monte Carlo calculations agree quant itatively with these experimental findings and predict a decrease of t he polarization towards zero at higher energies due to enhanced captur e into He+(4s). A positive polarization is also found for the Na I (3p --> 3s) target de-excitation. However, due to strong depolarization e ffects caused by the nuclear spin of the Na-23 nucleus it stays below 0.14.