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

Abstract

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.

Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence

“…We also account for the branching ratio between H and Ly radiation from the 3p state, and assume that light from the 3s state is unpolarized. Given our measured P 3 =P e ratio of 0.065 near threshold, and taking the relative initial populations of the three sublevels as those given for electron impact excitation of H [26], we obtain T 0 0:37. Assuming equal initial populations of the three substates, T 0 0:47.…”

Angular Momentum Partitioning in the Dissociation of Diatomic Molecules

“…Following dissociation, we assume that the atomic 3s, 3p, and 3d states all have equal spin polarization T', and that this polarization is completely coupled to the orbital angular momentum in the case of the 3p and 3d states, while we ignore hyperfine depolarization [12]. Taking into account the branching ratio between Hα and Lyα radiation (see Figure 3), assuming that light from the 3s state is unpolarized, and using published data for the relative production cross sections for 3s, 3p, and 3d states as the result of electron impact dissociation of H 2 [14], we can infer a threshold value of T' =0.37. Assuming that all three n=3 initial populations are equal, T' = 0.47.…”