Polarization of Light frome−−HeCollisions

The polarization of light resulting from the excitation of helium by electron impact has been measured as a function of electron energy. We report here our results in the energy threshold region for the following transitions: $3 {}_{}{}^1{}_{}{}^{}P\to 2 {}_{}{}^1{}_{}{}^{}S (\lambda =5016\mathrm{} \mathrm{\AA })$, $3 {}_{}{}^3{}_{}{}^{}P\to 2 {}_{}{}^3{}_{}{}^{}S (\lambda =3889\mathrm{} \mathrm{\AA })$, and $4 {}_{}{}^1{}_{}{}^{}D\to 2 {}_{}{}^1{}_{}{}^{}P (\lambda =4922\mathrm{} \mathrm{\AA })$. The results reported here are in substantial agreement with the results previously reported by McFarland. Also, no dependence of the polarization on the magnetic field parallel to the electron beam was observed.