POLARIZATION STUDIES OF LYMAN-ALPHA RADIATION EMITTED IN ATOM-H-2-MOLECULE COLLISIONS

A polarization study of Lyman-alpha radiation emitted in collisions of H+, H, He+, and He projectiles with H-2 molecules has been performed at projectile energies ranging from 1-25 keV. In H+ - H-2 and H - H-2 collisions, the measured linear polarization is negative at low incide nt velocities, indicating a preferred alignment of the excited electro n charge cloud perpendicular to the incident projectile direction. Thi s is taken as significance for a rotational coupling which in these tw o collision systems predominantly populates the H(2p +/- 1) substates. In He+ - H-2 and He - H-2 collisions, the measured linear polarizatio n is about zero and independent of the projectile energy. In these mor e asymmetric systems, a' - a' and a' - a" couplings are now of compara ble magnitude.