Fluorescence Polarization of Hydrogen and Deuterium Molecules Excited by Polarized Electron Impact

We report relative Stokes parameters for molecular and atomic transitions in H$_2$ and D$_2$ excited by spin-polarized electrons. Specifically, rotationally isolated transitions in the $d$ $^3\Pi_u$$1s\sigma3p\pi$ $\rightarrow$ $a$ $^3\Sigma_g^+$$1s\sigma2s\sigma$ band have been studied as well as Balmer-$\alpha$ excited fragments for both H and D. Values of the circular polarization fraction normalized to the incident electron spin polarization, P$_3$/P$_e$, for atomic emission (656 nm) from H and D are nearly equivalent ($\sim$0.08 near threshold), and higher values are found for the case of molecular fluorescence ($\sim$0.14 for H$_2$).