POLARIZATION OF LYMAN-ALPHA RADIATION FROM ATOMIC-HYDROGEN EXCITED BYELECTRON-IMPACT FROM NEAR-THRESHOLD TO 1800 EV

The polarization of Lyman-alpha radiation, produced by electron-impact excitation of atomic hydrogen, has been measured over the extended en ergy range from near threshold to 1800 eV. Measurements were obtained in a crossed-beam experiment using a silica-reflection linear polariza tion analyzer in tandem with a vacuum-ultraviolet monochromator to iso late the emitted line radiation. Comparison with various theoretical c alculations shows that the present experimental results are in good ag reement with theory over the entire range of electron-impact energies and, in particular, are in excellent agreement with theoretical conver gent-close-coupling (CCC) calculations performed in the present work. Our polarization data are significantly different from the previous ex perimental measurements of Ott, Kauppila, and Fite [Phys. Rev. A 1, 10 89 (1970)].