Polarization of Balmer-α radiation following electron impact on atomic hydrogen

The polarization of Balmer-α radiation excited in collisions of electrons with atomic hydrogen is presented for an electron energy range from threshold to 1000 eV. Measurements are in good agreement with calculations carried out using either convergent-close-coupling or R-matrix with pseudo-states approaches. Cascade is demonstrated to have a significant effect. Balmer-α excitation function data are also presented. A previous measurement of the polarization of Balmer-α following dissociative excitation of H₂ by electrons is confirmed and extended.