Alignment and orientation in He 2¹P and 3¹P excitation by electron impact

Abstract

The authors have studied the orientation and alignment of the 21P and 31P states of helium caused by electron impact at incident energies between 50 and 80 eV both experimentally and theoretically as a function of the electron scattering angle. The angular correlations between inelastically scattered electrons and VUV de-excitation photons were measured, particularly in the region where the orientation changes sign. The experimental results were compared with several distorted-wave models. The best of these models gave reasonably good agreement with the experimental data for excitation of the 21P and 31P states for scattering angles of less than 60 degrees and qualitative agreement for larger angles.