Polarization of Optical Radiation Induced by Electron Impact on Helium

Abstract

An investigation of the polarization of the atomic line radiation induced by electron impact on helium has been undertaken. Experimental data have been obtained on the polarization of several lines as a function of both electron energy and pressure. Secondary excitation processes, such as collision of the second kind and radiative transfer (cascade), are found to play an important role in the polarization. Expressions are derived for the analysis of the pressure effects on the polarization. Gas-kinetic collision cross sections involving atoms in excited states have been determined by observing the depolarization as the gas pressure increases.