Polarized Fluorescence from Nitrogen Molecules Excited by Polarized Electron Impact

We have measured the optical excitation function and relative Stokes parameters for 388$\pm $5 nm fluorescence from spin-polarized electron impact excitation of molecular N$_{2}$. Specifically, the circular polarization fraction normalized to the incident electron spin, P$_{3}$/P$_{e}$, was found to be +1(5){\%} at an electron energy of 30eV. This result, even though it contains contributions from 6 different triplet spectral lines, is consistent with the data of the M\"{u}nster group [1] who measured the N$_{2}$ 337 nm C$_{3}\Pi _{u}$ - B$_{3}\Pi _{g }(\nu '$=0, $\nu $=0) transition and found P$_{3 }<$ 0.002 at an energy of 14.5 eV. However the N$_{2}$ results are significantly different from the H$_{2}$ target case which gives P$_{3}$/P$_{e}$ of $\sim $10{\%} [2]. [1] C. Mette \textit{et al}., Verhandl. DPG (VI) \textbf{29}, 462 (1994). [2] A.S. Green \textit{et al}., Phys. Rev. Lett. \textbf{92}, 093201 (2004).