Experimental and theoretical studies of the electron impact alignment and orientation of the 2¹P state of helium below the ionisation threshold

Abstract

The alignment and orientation of the 21P state of helium by electrons of incident energy 24.0 eV has been studied both experimentally and theoretically. Experimentally, the angular correlation between the 2.8 eV scattered electron which has excited the state and the 58.4 nm photon resulting from its decay has been measured for electron scattering angles up to 120 degrees . Theoretically, the alignment and orientation parameters have been calculated using a five-state R-matrix method. There is excellent agreement between theory and experiment at all scattering angles.