Polarized Fluorescence from H$_2$ and D$_2$ Excited by Polarized Electron Impact

We report relative Stokes parameters for the following rotationally isolated molecular Fulcher band transitions in H$_2$ and D$_2$ excited from singlet ground states by spin-polarized electrons: \begin{center} \vspace{-.2cm} H$_2$ $d\:^3\Pi_u^-(v'=0)$ $\rightarrow$ $a\:^3\Sigma_g^+(v''=0)$ $+$ $\gamma(601.83$ nm$)$ $Q(1)$ \\ H$_2$ $d\:^3\Pi_u^-(v'=2)$ $\rightarrow$ $a\:^3\Sigma_g^+(v''=2)$ $+$ $\gamma(622.48$ nm$)$ $Q(1)$ \\ H$_2$ $d\:^3\Pi_u^-(v'=2)$ $\rightarrow$ $a\:^3\Sigma_g^+(v''=2)$ $+$ $\gamma(623.84$ nm$)$ $Q(3)$ \\ H$_2$ $d\:^3\Pi_u^+(v'=2)$ $\rightarrow$ $a\:^3\Sigma_g^+(v''=2)$ $+$ $\gamma(618.30$ nm$)$ $R(1)$ \\ $\;$D$_2$ $d\:^3\Pi_u^-(v'=0)$ $\rightarrow$ $a\:^3\Sigma_g^+(v''=0)$ $+$ $\gamma(600.68$ nm$)$ $Q(3)$. \end{center} \vspace{-.2cm} Values of the circular polarization fraction normalized to the incident electron spin polarization, P$_3$/P$_e$, for the above $Q(1)$ transitions are found to be ${\sim}0.15$, and smaller values are measured for the $Q(3)$ lines. For the $R(1)$ case, somewhat larger values of ${\sim}0.20$ are obtained.