Polarization of theλ=5876Å andλ=6679Å Lines in Helium Excited by Electrons

The polarization of the lines $\lambda =5876\mathrm{}$ Å and $\lambda =6679\mathrm{}$ Å resulting from the excitation of helium by electrons was measured as a function of the bombarding electron energy. The dependence of the polarization on the helium pressure is also reported for these lines. The observations reported here conflict with the theory of the polarization of collision-induced radiation at the threshold energy for excitation.