Polarization of Light Resulting from the Excitation of Helium by Electrons

Abstract

The polarization of light resulting from the excitation of helium by electrons was measured as a function of the bombarding electron energy. The wavelengths of the light whose polarization was measured are as follows: $\lambda =4713\mathrm{} \AA (4\mathrm{}{}_{}{}^3{}_{}{}^{}S\to 2{}_{}{}^3{}_{}{}^{}P)$, $\lambda =4922\mathrm{} \AA (4\mathrm{}{}_{}{}^1{}_{}{}^{}D\to 2{}_{}{}^1{}_{}{}^{}P)$, $\lambda =3188\mathrm{} \AA (4\mathrm{}{}_{}{}^3{}_{}{}^{}P\to 2{}_{}{}^3{}_{}{}^{}S)$, $\lambda =5876\mathrm{} \AA (3\mathrm{}{}_{}{}^3{}_{}{}^{}D\to 2{}_{}{}^3{}_{}{}^{}P)$, $\lambda =4388\mathrm{} \AA (5\mathrm{}{}_{}{}^1{}_{}{}^{}D\to 2{}_{}{}^1{}_{}{}^{}P)$, $\lambda =5016\mathrm{} \AA (3\mathrm{}{}_{}{}^1{}_{}{}^{}P\to 2{}_{}{}^1{}_{}{}^{}S)$, $\lambda =4471\mathrm{} \AA (4\mathrm{}{}_{}{}^3{}_{}{}^{}D\to 2{}_{}{}^3{}_{}{}^{}P)$, $\lambda =3889\mathrm{} \AA (3\mathrm{}{}_{}{}^3{}_{}{}^{}P\to 2{}_{}{}^3{}_{}{}^{}S)$. The polarization curves for the different wavelengths were measured for different pressures of the helium gas, and for $\lambda =4922\mathrm{} \AA , 4388 \AA , \mathrm{and} 5016 \AA$, there is a marked pressure dependence. There is a decided discrepancy between the theory as summarized by Percival and Seaton and the experimental results presented in this paper. No resolution of this discrepancy is given at this time.