Polarization of Balmer-alpha radiation following electron impact on atomichydrogen

The polarization of Balmer-alpha radiation excited in collisions of electro ns with atomic hydrogen is presented for an electron energy range from thre shold to 1000 eV. Measurements are in good agreement with calculations carr ied out using either convergent-close-coupling or R-matrix with pseudo-stat es approaches. Cascade is demonstrated to have a significant effect. Balmer -alpha excitation function data are also presented. A previous measurement of the polarization of Balmer-alpha following dissociative excitation of H- 2 by electrons is confirmed and extended.