Alignment and orientation in the electron-impact excitation of the2P1state of He from 40 to 500 eV

Abstract

Electron-photon angular correlations between electrons which have excited the $2{}_{}{}^1{}_{}{}^{}P$ state of He and photons from the $2{}_{}{}^1{}_{}{}^{}P\to 1{}_{}{}^1{}_{}{}^{}S$ transition have been studied for 100-, 200-, and 500-eV incident electrons. Values of $\lambda$ and $\left|\chi \right|$ obtained from these measurements are compared to values which have been obtained in other experiments and calculations. The results are in good agreement with the recent distorted-wave calculation of Madison. The values of $\lambda$ and $\left|\chi \right|$ from all experiments have been combined to examine the behavior of the Fano-Macek alignment and orientation parameters for electron energies from 40 to 500 eV.