Experimental and (first-order many-body) theoretical differential and integral cross sections for excitation of the n=3 states of He by electron impact at 29.2 and 39.7 eV

Abstract

Differential and integral electron scattering cross sections have been measured and calculated for the transitions 1S1→3S1,3P3 and for the experimentally unresolved transitions 1S1→3P1,3D1,3 in helium. Measurements were made relative to both the 2P3 and 2P1 transitions at incident electron energies of 29.2 and 39.7 eV, and over the angular range 5-136°. The n=3 relative differential cross sections (DCS) were normalized to the absolute scale by utilizing known normalized absolute DCS for the 2P3 and 2P1 transitions. The theoretical calculations were carried out in the first-order manybody theory of Csanak, Taylor, and Yaris. Comparisons are also made of the present measurements and calculations with other calculations carried out for the 3S1, 3D1, and 3P1 states in the Born and several Ochkur-like approximations. The theoretical origins in several theories of the intriguing sharp minimum in the 1S1→3S1 DCS are discussed. © 1975 The American Physical Society.